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Biomedical subjects

P Perlmann

Publications and source records attributed to P Perlmann.

At least 145 records · Page 8Linked to original sources
PubMed1986

Separation of human B lymphocytes on Helix pomatia A haemagglutinin into two major fractions differing in responsiveness to T-dependent mitogen (pokeweed mitogen) or antigen (tetanus toxoid).

A B-cell fraction consisting of 70% of cells carrying the B-cell-associated B1 antigen, 15-20% of M1+ non-B cells, and less than 3% of T cells was prepared from the peripheral blood of healthy human donors, previously vaccinated with tetanus toxoid (TT). As assessed by immunofluorescence after treatment with neuraminidase, approximately 40-50% of the B cells had surface structures binding to Helix pomatia A haemagglutinin (HP). The cells were separated into three fractions by affinity chromatography on HP conjugated to Sepharose (P, non-retained cells; EI, cells eluted with 0.1 mg/ml N-acetyl-D-galactosamine (D-GalNac); EII, cells eluted with 1 mg D-GalNac/ml). The majority of B cells in fraction EII were HP+ and were rich in cells expressing the B2 differentiation antigen. Sixty per cent of the B cells in this fraction also expressed the major HP-binding glycoprotein, gp 150. In the presence of autologous T cells, these B cells were strongly responsive to activation by either pokeweed mitogen (PWM) or antigen (TT), as reflected by differentiation into plasma cells, secretion of polyclonal IgG and IgM, or IgG anti-TT antibodies. In contrast, fraction P, which contained more than 90% HP-B cells, and which was partially depleted of B2+ cells, responded poorly or not at all to both PWM and TT. Fraction EI was a mixed fraction that responded in an intermediate fashion. When the preparations were depleted of contaminating non-B cells carrying the monocyte or large granular lymphocyte associated M1 antigen, their response to the two stimulating agents did not alter. The results suggest that HP+ B cells differ from HP-B cells in their responsiveness to T-cell signals. Fractionation on unsolubilized HP offers a simple and efficient way of separating B cells into at least two subsets differing in their responsiveness to T-cell-derived differentiation and maturation signals.

Animals↗
PubMed1986

Anti-Plasmodium falciparum antibodies acquired by residents in a holoendemic area of Liberia during development of clinical immunity.

Sera from 48 children and adolescents (2-15 years of age), residing in a malaria holoendemic area of Liberia were investigated for specificities and isotypes of anti-P. falciparum antibodies. No clear-cut relationship to the development of clinical immunity was found when the overall antibody activities to total parasite antigens were determined by enzyme-linked immunosorbent assay (ELISA). Although there was a certain rise of IgM, total IgG- and IgG2 antibody activities, this was most pronounced at ages when a clinical but nonsterile immunity is already present. When the sera were investigated by immunoprecipitation of 35S-methionine labeled parasite polypeptides, the total number of parasite antigens precipitated was similar at all ages. Analysis by indirect immunofluorescence (IFA), registering antibodies to intracellular parasite antigens, revealed no age-dependent changes in antibody titers. In contrast, when the sera were assayed by a novel IFA, specific for a restricted number of parasite antigens in the membrane of infected erythrocytes, the frequency of positive sera as well as the anti-P. falciparum titers rose in parallel with the development of clinical immunity. Thus, these antigens appeared to be important inducers of protective immune responses and may be suitable candidates for a vaccine against the asexual blood stages of P. falciparum.

Adolescent↗
PubMed1986

Characterization of the humoral immune response in Plasmodium falciparum malaria. III. Factors influencing the coexpression of antibody isotypes (IgM and IgG-1 to 4).

Isotypes (IgM and IgG-1 to 4) of anti-P. falciparum antibodies were investigated in sera of malarial patients or immune donors by enzyme linked immunosorbent assay (ELISA) and two indirect immunofluorescence assays (IFAs), one staining intra-erythrocytic parasites of all stages and the other a restricted number of parasite antigens deposited in the membrane of infected erythrocytes by invading merozoites (Perlmann & Wahlgren, 1983; Perlmann et al., 1984, Wahlgren et al., 1985a). There was no correlation in overall antibody titres between the two IFAs. Antibodies of both IgM and all four IgG isotypes were detected in both assays. With the IFA for intracellular parasites a brilliant fluorescence was obtained with antibodies of all isotypes. However IgG-2 antibodies often gave staining restricted to the surface of schizonts. The incidence and reactivity in individual sera of antibodies of the different isotypes did not relate to the immune status of the donors (acute infection or clinically immune) but related well to the degree of malarial exposure as reflected by the overall antibody titres. This, in all three assays, high titred sera frequently contained antibodies of all isotypes while low titred sera usually only contained antibodies of IgM, IgG-1 and IgG-3 isotype. On average, the overall expression of antibodies of different isotypes in individual sera appears to reflect a sequential downstream (5' to 3') activation of the corresponding Igh-C genes in P. falciparum specific B-cell clones.

Adolescent↗
PubMed1985

The large sialoglycoprotein of human lymphocytes. I. Distribution on T and B lineage cells as revealed by a monospecific chicken antibody.

Chickens were immunized with highly purified large sialoglycoprotein of human lymphocytes (L-LSGP; gp 150) which was isolated from neuraminidase-treated normal peripheral blood lymphocytes by affinity chromatography to HP-Sepharose and further purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Antibodies isolated from plasma and egg yolk were highly specific for desialylated L-LSGP (apparent molecular mass approximately 150 kDa). The antigenic sites recognized by the antibodies are probably located in the peptide moiety of the molecule since antibody binding to lymphocytes was not inhibited by a variety of different sugars or abrogated by absorption on various erythrocytes. In immunofluorescence experiments, greater than or equal to 75% of neuraminidase-treated thymocytes and peripheral blood lymphocytes, virtually all E+ cells and T4+ or T8+ T chronic lymphocytic leukemia (CLL) cells were stained by anti-gp 150. A small fraction (approximately 10%) of thymocytes and a larger fraction (greater than or equal to 30%) of T CLL cells in some patients were stained before neuraminidase treatment. Thymocytes appear to contain considerably lower amounts of a less sialylated form of L-LSGP than peripheral blood lymphocytes. In contrast to blast cells of 5-day concanavalin A or leucoagglutinin cultures (greater than or equal to 90% anti-gp150+) only about 50% of the blast cells generated in 5-day mixed leukocyte cultures were anti-gp150+. The large majority (greater than or equal to 75%) of both the anti-gp150+ and anti-gp150- cells were T3+ and T11+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The large sialoglycoprotein of human lymphocytes. II. Biochemical features.

Large sialoglycoprotein of human lymphocytes (L-LSGP) from thymocytes and from peripheral blood lymphocytes (PBL) of normal donor and of B chronic lymphocytic leukemia (CLL) patients was purified by affinity chromatography to Maclura pomifera agglutinin (MPA)-Sepharose followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). L-LSGP from the three different sources was very similar in amino acid composition. It contained a high proportion of acidic and hydroxy amino acids and also significant amounts of cysteine. No reduction in mobility in SDS-PAGE was noted for unreduced L-LSGP. The molecule may already in its native form have an extended conformation containing either free sulfhydryl groups or small S-S loops not affecting mobility in SDS-PAGE. L-LSGP was found to be highly glycosylated, the thymocyte glycoprotein containing somewhat less carbohydrate by weight (44%) than that of PBL (normal PBL 53% and B CLL 52%). This was due primarily to a lower content of sialic acid. The molecules contained mannose, galactose, N-acetyl galactosamine, N-acetylglucosamine and sialic acid in molar ratios 1.0:3.0:1.1:1.2:1.3 (thymocyte L-LSGP), 1.0:3.8:1.2:1.0:1.7 (PBL L-LSGP) and 1.0:3.5:2.2:1.3:2.8 (B CLL L-LSGP). The weak interaction of L-LSGP with lentil lectin, concanavalin A (Con A) and leucoagglutinin (La), its unchanged mobility in SDS-PAGE after tunicamycin treatment and its high amount of hydroxy amino acids suggest that most carbohydrate chains are O-glycosidically linked to the peptide chain. Native as well as Nase-treated L-LSGP show size microheterogeneity. This is probably due to small chemical differences in the L-LSGP molecules from different lymphocyte subsets.

Amino Acids↗
PubMed1985

Tumour inhibitory effects of TCGF/IL-2/-containing preparations.

Supernatants from ConA-stimulated rat spleen cell cultures and from cultures of PMA-stimulated murine lymphoma subline EL-4TF were found to contain TCGF and to inhibit growth of a transplantable, MC-induced sarcoma MC11 in syngeneic mice. Tumour-inhibitory effects of the supernatants were dependent on local and repeated administration. Prior to use of the supernatants obtained from PMA-stimulated EL-4TF cell cultures, the dialysable PMA had to be removed; contamination with PMA was found to abolish the tumour-inhibitory effect of the supernatants and to produce enhancement of tumour growth. A significant tumour-inhibitory effect has also been obtained with partially purified TCGF prepared from culture supernatants of cloned EL-4TF cells by ammonium sulphate precipitation, ion-exchange (FPLC) chromatography, and AcA 44 Ultrogel filtration.

Animals↗
PubMed1985

A p50 surface antigen restricted to human urinary bladder carcinomas and B lymphocytes.

We have previously described the derivation of a monoclonal antibody, S2C6, to a novel 50 Kdalton antigen associated with human urinary bladder carcinoma. No reactions were obtained with carcinomas of unrelated origin or with normal urothelial cells. However, the antibody also reacted with a similar antigen on some cell lines of B lymphocyte origin. Using large panels of target cells we have now shown that this reactivity was entirely restricted to cells of the B lineage within the haematopoietic system. As opposed to its apparent restriction to malignant cells of the urothelium, the S2C6 antigen was expressed by normal B lymphocytes as well as by many malignant B cells (chronic lymphocytic leukaemia, hairy cell leukaemia and immunocytoma). Pre-B cells derived from acute lymphocytic leukaemia and plasma cells from multiple myeloma lacked the antigen. Expression was significantly enhanced on cultured B cells from Burkitt lymphomas and on Epstein-Barr virus-transformed lymphoblastoid cell lines including those of the pre-B phenotype derived from fetal bone marrow. As judged from the molecular size and the distribution pattern displayed by the S2C6 antigen it appears to be distinct from other B cell antigens previously described. A possible relation of the S2C6 antigen to a receptor for B cell growth factors is discussed.

Antibodies, Monoclonal↗
PubMed1985

A new surface marker on equine peripheral blood lymphocytes. I. Subpopulations of lymphocytes with receptors for Helix pomatia A hemagglutinin (HP).

Untreated and neuraminidase-treated equine peripheral blood lymphocytes were analysed for binding of the A hemagglutinin of the snail Helix pomatia (HP). For optimal staining by direct immunofluorescence, the concentration of neuraminidase had to be increased as compared to that needed for other species. Moreover, higher concentrations of HP were required for optimal staining of equine lymphocytes as compared to lymphocytes from other species. Even so, the maximal number of equine lymphocytes exhibiting positive staining was only about 20%. No, or very few, HP-positive lymphocytes were seen when neuraminidase treatment was omitted. However, when the more sensitive method of indirect immunofluorescence was used, approximately 60% of the lymphocytes were HP positive without prior treatment with this enzyme. Neuraminidase treatment significantly increased this figure to about 75%. In all instances, HP binding was specific since it was inhibited by the competitive sugar hapten N-acetyl-D-galactosamine (D-GalNAc) while addition of D-glucose (D-Glc) gave no inhibition. HP binding to neuraminidase-treated lymphocytes was also investigated quantitatively by means of 125I-labeled HP. The number of HP molecules bound per HP-positive cell was approximately 3 X 10(5) and the apparent association constant for the binding of HP to its cellular receptors was approximately 8 X 10(7) 1/mol. No binding of HP to untreated lymphocytes could be recorded in these experiments.

Animals↗
PubMed1985

A new surface marker on equine peripheral blood lymphocytes. II. Characterization and separation of purified blood lymphocytes with receptors for Helix pomatia A hemagglutinin (HP).

In a preceding report we have shown that the lectin Helix pomatia A hemagglutinin (HP) binds to two subpopulations of neuraminidase-treated equine peripheral blood lymphocytes (PBL), constituting about 20% and 75% of PBL, respectively. The aim of the present study was to further characterize these HP+ cells in regard to other surface markers such as receptors for guinea pig erythrocytes (GPR+ cells), membrane-bound immunoglobulins (sIg+ cells), receptors for activated complement (C3R+ cells) and receptors for IgG (Fc alpha R+ cells). This was done by double marker analysis and by lymphocyte fractionation either on columns charged with HP coupled to Sepharose beads or by rosetting with guinea pig erythrocytes. The fractions were also analysed for their proliferative response in the mixed lymphocyte tumor cell interaction (MLTC) assay and to the mitogens leucoagglutinin (La) and concanavalin A (Con A). The results revealed that the majority of GPR+ cells also expressed high avidity receptors for HP, as defined by means of direct immunofluorescence. These cells constituted a subpopulation of GPR+/HP+ cells T cells comprising approximately 20% of PBL. In contrast, about 75% of the HP+ cells in indirect immunofluorescence were GPR-. The fractionation experiments showed that HP+ and GPR+ cells were probably not B cells since they were sIg-. The C3R+ and Fc alpha R+ lymphocytes were heterogeneous in regard to HP receptors but the majority of these cells was also found in the fractions depleted of HP+ and GPR+ lymphocytes. The fractions eluted from HP columns gave a strong proliferative response in MLTC, whereas fractions depleted of HP+ cells responded poorly. However, in contrast to the GPR+-depleted fractions, those enriched in GPR+ lymphocytes responded poorly to the T cell mitogens La and Con A. The mitogenic response of the HP-column fractions to La and to Con A was variable. The results are discussed in relation to HP being a surface marker for a heterogeneous population of equine T cells.

Animals↗
PubMed1985

Monoclonal antibodies against human urinary bladder carcinomas: selectivity and utilization for gamma scintigraphy.

Mouse monoclonal antibodies to human urinary bladder carcinoma cells have been examined by indirect membrane immunofluorescence using a panel of 27 human cell lines. Two of the monoclonal antibodies, 7E9 (IgG3) and S2C6 (IgGl), were found to distinguish between urinary bladder carcinoma cells and normal urothelium. The third monoclonal antibody, T24.06.5(IgGl), discriminated among cell lines of urothelial and non-urothelial origin but did not distinguish between urinary bladder carcinoma and normal urothelial cells. None of the of the antibodies was found to be strictly selective, and occasional cross-reactions with unrelated cell types were observed. The monoclonal antibody 7E9, showing the highest degree of selectivity, was further examined by an indirect immunoperoxidase technique on frozen tissue sections from 19 patients. The antibody reacted with all (7/7) bladder carcinomas examined and gave negative results with control normal bladder mucosa (0/8) and unrelated tumor tissue (0/4) sections. The 7E9 antibody was purified by protein A affinity chromatography, labeled with 131I and used for gamma-scintigraphy in nude mice xenografted with human urinary bladder carcinoma T24. The 7E9 antibody was capable of locating the T24 xenografts in nude mice; it localized preferentially in the T24 tissue compared to normal mouse tissues. The T24 xenografts could not be detected by gamma-scintigraphy with 131I-labeled monoclonal antibody against human mammary carcinoma cells and two other control antibodies. Likewise the 131I-labeled 7E9 antibody was not capable of locating human mammary carcinoma xenografts in nude mice.

Animals↗
PubMed1985

Specificities and binding properties of 2 monoclonal antibodies against carcinoma cells of the human urinary bladder.

Mice were immunized with cultured cells derived from transitional cell carcinoma of the human urinary bladder (TCC). Spleen cells were fused with mouse myeloma cell line Sp2/0-Ag14 and the hybridomas obtained screened for antibody production against a panel of human cells. Two hybridomas were selected for further studies. The antibodies from one of these hybridomas (P7A5-4) could clearly discriminate between malignant and normal cells from the bladder, both when tested with cultured cells and fresh tissue. The P7A5-4 antibodies, however, also reacted with some non-TCC cultured carcinoma and melanoma cells but to a lesser extent. This difference in reactivity was even more pronounced in the fresh tumours tested, thus indicating a quantitative difference in antigen expression between TCC and other cells. From extracts of TCC cells, P7A5-4 bound three polypeptides of mol. wts 92Kd (ConA+), 23 and 17Kd (ConA-). The antibody derived from hybridoma SK4H-12 bound a ConA reactive glycopeptide of 100Kd mol. wt, the expression of which was almost entirely restricted to urothelial cell lines and tissue of TCC origin, as shown by immunocytochemical studies. The finding in this study of new antigens associated with urinary bladder carcinoma, extend the results obtained previously in our laboratory (Koho et al., 1984; Paulie et al., 1984) and further delineate the heterogeneity of tumour-associated antigens in this human tumour system.

Animals↗
PubMed1985

Natural cytotoxicity of human lymphocytes against equine target cells in vitro.

Human lymphocytes displayed a frequent natural cytotoxicity (NK) in vitro against normal equine dermal fibroblasts (ED) and against equine tumour cells of a virus-containing cell line (Mc-1). Similarly, human normal sera contained antibodies that induced antibody-dependent cellular cytotoxicity (ADCC) by normal human lymphocytes against the same target cells. Both NK and ADCC varied for different donors. For individual donors, however, cytotoxicity against the two target cells was significantly correlated both in NK and ADCC. For ED there was also a significant correlation between ADCC and NK activity. Both NK and ADCC showed some selectivity as assessed by cold target cell inhibition. Inhibition studies with Fab fragments of anti-human IgG established the involvement of immunoglobulins in the NK reaction. In this context, a marked and mainly immunoglobulin-dependent increase in both NK and ADCC activity against Mc-1 was observed in a laboratory worker frequently exposed to the target cells. The results indicate that variations of natural cytotoxicity in individual donors may sometimes be an indication of an ongoing spontaneous sensitization.

Animals↗
PubMed1985

Mumps virus-induced enhancement of the in vitro cytotoxicity of cord blood lymphocytes.

Purified lymphocytes from the umbilical cord of healthy donors (CBL) displayed lower natural cytotoxicity (NK) and antibody-dependent cellular cytotoxicity (ADCC) than peripheral blood (PBL) from adult donors. In contrast, CBL treated with small amounts of UV-inactivated or live mumps virions expressed the same level of enhanced cytotoxicity (virus-dependent cytotoxicity (VDCC)) against non-infected target cells as PBL. For individual CBL donors there was no correlation between the level of NK and VDCC, indicating involvement of partly distinct effector cell populations. The heterogeneity of the effector cells active in VDCC was confirmed by cell fractionation experiments. The major CBL effector cells in NK and ADCC were found in 'non-T' lymphocyte fractions and/or in fractions containing cells with high-avidity receptors for IgG. In contrast, CBL fractions consisting of about 100% lymphocytes bearing T-cell markers and depleted of Fc gamma R+ cells were strongly cytotoxic in VDCC when T24 cells (human bladder carcinoma) were the targets. With two other target cell types of similar susceptibility to VDCC, the cytotoxic activity of T-cell-containing fractions was less pronounced, indicating that the target cells play an active role in effector cell selection. The surface marker profiles of the VDCC effector cells were the same for CBL and adult PBL. Incubation of CBL with UV-inactivated virions usually gave no significant stimulation of DNA synthesis above that seen in virus-free controls. Taken together, our results suggest that neither specific recognition of viral antigen by T cells nor mitogenic effects of viral material are involved in VDCC generation.

Adult↗
PubMed1985

Virus-dependent cellular cytotoxicity in vitro. Mechanisms of induction and effector cell characterization.

When human peripheral blood lymphocytes were incubated with 51Cr-labelled tissue culture cells (T24 bladder carcinoma cells or Chang liver cells), their natural cytotoxicity (NK) usually stopped after 8 h of incubation. The 51Cr release induced by lymphocytes treated with small amounts of live or ultraviolet-inactivated mumps virus was strongly enhanced and lasted longer. When the lymphocytes were fractionated by Percoll gradient centrifugation, the highest NK activity was found in the low-density fraction enriched in large granular lymphocytes, whereas that of the T-cell-enriched high-density fractions was low. In contrast, the virus-dependent cellular cytotoxic (VDCC) activity was more evenly distributed between these fractions. However, there was a difference between the target cells in that the T24 cells were more susceptible to the cytotoxicity of lymphocytes in the high-density fractions than the Chang cells. Studies of Percoll fractions in the single-cell agarose assay showed that virus treatment increased the proportion of both target binding cells and killer cells in all fractions. Moreover, in the high-density fractions the increase in the number of killer cells was greater than that in binding cells, suggesting that the enhanced target cell killing induced by the virions reflected both increased binding and effector cell activation. Surface marker analysis of unfractionated lymphocytes indicated that the number of T3+ effector cells was greater than that of the HNK-1+ effector cells, regardless of whether the lymphocytes were treated with virus or not. However, for both NK and VDCC, the T3 to HNK-1 distribution ratio on the effector cells was 5-8:1 for T24 and 2:1 for Chang. Taken together, the results indicate that both NK and VDCC effector cells are phenotypically heterogeneous and that the target cells may play an active role in the recruitment of those effector cells that are most efficient in that system. The enhancement of lymphocyte cytotoxicity primarily reflects effector cell recruitment.

Antibodies, Monoclonal↗
PubMed1985

The role of serologically defined epitopes on mumps virus HN-glycoprotein in the induction of virus-dependent cell-mediated cytotoxicity. Analysis with monoclonal antibodies.

The importance of virus structural proteins for the induction of virus-dependent cellular cytotoxicity (VDCC) was studied by means of monoclonal antibodies raised in mice against mumps virions. Antibodies against the viral glycoprotein bearing the haemagglutination and neuraminidase activities (HN) inhibited VDCC but not the natural cytotoxicity (NK) displayed by the lymphocytes in the absence of virus. Antibodies to the fusion factor, the membrane protein or the nucleoprotein were inactive. These results confirmed our previous conclusion, that the only viral component required for VDCC induction is the HN protein. To clarify the role of this protein in VDCC further, the inhibitory activity of 13 HN-specific monoclonals, all of IgG isotype and directed against 9 distinct determinants, was studied in detail. Seven antibodies reacting with 3 different determinants of the peptide moiety of the HN protein were strongly inhibitory. The remaining antibodies, specific for 5 additional peptide epitopes, had intermediate or weak inhibitory effects. One carbohydrate specific anti-HN antibody was inactive although its antigen-binding capacity was of the same magnitude as that of a good inhibitory antibody. The anti-HN antibodies inhibited VDCC regardless of their IgG subclass. Moreover, VDCC inhibition was not correlated with the capacity of the antibodies to inhibit haemagglutination, haemolysis, neuraminidase activity, or the infectivity of the virus. These results suggest that full expression of VDCC requires the interaction of more than one of the serologically defined structures of the HN polypeptide with virus receptors on the lymphocytes and probably also on the target cells. These structures may be different at least in part from those involved in other known biological activities of the virus. Treatment of lymphocytes with virus increases both the number of target-binding cells (TBC) and the number of cytotoxic effector cells. However, when treated under conditions which gave optimal VDCC inhibition, none of the inhibitory antibodies reduced the virus-mediated increase in TBC. This indicates either that the anti-HN antibodies decreased the efficiency of effector-target cell interaction necessary for VDCC induction, or that they blocked a post-binding step required for triggering of cytotoxicity.

Animals↗
PubMed1985

Tumour localization of radiolabelled monoclonal antibody in mice bearing human urinary bladder (T24) carcinoma xenografts.

Selectivity of mouse monoclonal antibody 7E9 (IGG3) directed against human urinary bladder carcinoma cells has been examined by indirect membrane immunofluorescence, using a panel of 31 human cell lines. The 7E9 monoclonal antibody discriminated between urinary bladder carcinoma cells and normal urothelium or cells of non-urothelial origin, although occasional reactions with bladder carcinoma-unrelated cell types were observed. The 7E9 antibody was purified by protein A affinity chromatography, labeled with 131I and used for gamma scintigraphy in nude mice xenografted with human urinary bladder carcinoma T24. The 7E9 antibody was capable of locating the T24 xenografts in nude mice; it localized preferentially in the T24 tissue compared to normal mouse tissues. The T24 xenografts could not be detected by gamma scintigraphy with 131I-labelled monoclonal antibody against human mammary carcinoma cells and two other control antibodies. Likewise, the 131I-labelled 7E9 antibody was not capable of locating human mammary carcinoma xenografts in nude mice.

Animals↗
PubMed1985

Pf 155, a candidate for a blood stage vaccine in Plasmodium falciparum malaria.

Pf 155 is a Mr 155,000 P. falciparum antigen, which is deposited in the erythrocyte membrane at merozoite invasion. The antigen is detected by a modified immunofluorescence assay giving staining of the surface of ring stage infected erythrocytes. Cell lines producing human monoclonal antibodies to Pf 155 were established and two different antibodies of IgM and IgG class, respectively, were characterized further. Both antibodies gave a strong surface immunofluorescence and in immunoblotting they react strongly with Pf 155, but also with some lower molecular weight material, including polypeptides of Mr 135,000 and 120,000. Both antibodies were efficient inhibitors of P. falciparum reinvasion in vitro. Pf 155 as well as the Mr 135,000 and 120,000 polypeptides were shown to bind with high affinity to human erythrocyte glycophorin. An octapeptide (GluGluAsnValGluHisAspAla) corresponding to a repeated sequence in Pf 155 was synthesized. Rabbit antibodies to the octapeptide gave a distinct surface immunofluorescence and reacted with Pf 155 and the Mr 135,000 and 120,000 polypeptides in immunoblotting. Human antibodies reacting with the octapeptide were isolated by affinity chromatography from the serum of a P. falciparum immune individual. These antibodies showed a strong reaction with Pf 155 as determined by immunoblotting and surface immunofluorescence. Pf 155 reactive antibodies affinity purified on monolayers of P. falciparum infected erythrocytes are very efficient inhibitors of parasite reinvasion. Such antibody preparations depleted of octapeptide reactive antibodies showed a markedly decreased reinvasion inhibitory capacity, while a high inhibitory activity was recovered in the octapeptide reactive antibodies. Pf 155 fulfills several criteria thought to be proper for antigens involved in anti-malarial protective immunity.

Amino Acid Sequence↗