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Biomedical subjects

L Chess

Publications and source records attributed to L Chess.

At least 73 records · Page 4Linked to original sources
PubMed1985

The isolation and nucleotide sequence of a cDNA encoding the T cell surface protein T4: a new member of the immunoglobulin gene family.

The surface glycoproteins T4 and T8 define different functional subsets of T lymphocytes and may act as recognition molecules mediating appropriate interactions between the T cell and its target. Previously we employed gene transfer and subtractive hybridization to isolate a T8 cDNA; now we have isolated and sequenced a cDNA clone encoding the T4 molecule. The deduced protein sequence reveals that T4 is an integral membrane protein that shares significant amino acid and structural homologies with members of the immunoglobulin supergene family. The overall structure of T4 consists of an N-terminal variable (V)-like domain, a joining (J)-like region, a third extracellular domain, a membrane-spanning region homologous to class II MHC beta-chains, and a highly charged cytoplasmic domain. Comparison of the protein sequences deduced from the T4 and T8 cDNAs reveals structural similarities consistent with their postulated role as recognition molecules, as well as differences suggesting that the two proteins recognize different structures on the target cell.

Amino Acid Sequence↗
PubMed1984

Accelerations of the human fetal heart rate at 38 to 40 weeks' gestational age.

In order to document the normal structure and pattern of fetal heart rate accelerations near term, we measured fetal heart rate and fetal movements for 24-hour observation intervals in 12 healthy pregnant women at 38 to 40 weeks' gestation. There were 34 accelerations per hour on the average with a mean amplitude of 22.8 bpm and a mean duration of 40.7 seconds. The longest time between successive accelerations was 37 minutes. There was a significant negative correlation between the mean daily maximum amplitude of accelerations and the mean daily fetal heart rate (r = -0.84). Fetal heart rate acceleration patterns suggested a prolonged period of fetal wakefulness during the late evening.

Electrocardiography↗
PubMed1984

Construction of human T-cell hybrids with helper function.

Human T-cell hybrids with helper activity were obtained after fusion of phytohemagglutinin-activated normal human T cells with a 6-thioguanine-resistant, aminopterin-sensitive human T-cell line. This mutant line, designated CEM-T15, was derived from the human T-cell line CEM after mutagenesis with ethyl methanesulfonate. The polyethylene glycol induced fusion and the selection in hypoxanthine- aminopeterin -thymidine medium were performed by modification of standard somatic cell hybridization techniques. After fusion, the strategy for selecting hybrids consisted in screening growing cultures for the presence of cells expressing the OKT3 cell surface differentiation antigen. OKT3 was chosen because it is present in 85-95% of normal human T cells but absent from CEM-T15 cells. Thus, OKT3+ cells growing 5-7 weeks after fusion most likely represented hybrids between normal T cells (OKT3+) and continuously growing CEM-T15 cells (OKT3-). Several of the hybrids were tested for their capacity to promote pokeweed mitogen-induced antibody production by B cells. These experiments demonstrated that many of the hybrids had helper activity. Periodical testing of these uncloned hybrids for helper activity revealed functional instability, with most of the hybrids losing helper activity after 20 weeks of continuous culture. However, early and repeated cloning of the same hybrids resulted in a series of hybrid clones with helper activity still present more than 8 months after fusion. In more recent fusions, we have demonstrated that human helper hybrids producing helper factor(s) can also be obtained. These and similar hybrids with different functions will be of considerable importance in further studies of the immunobiology of human T lymphocytes.

Antigens, Surface↗
PubMed1984

Functional analysis of human T cell subsets defined by monoclonal antibodies. VI. Distinct and opposing immunoregulatory functions within the OKT8+ population.

In the present study, we investigated the immunoregulatory potential of OKT8+ cells after in vitro activation. Initial studies had demonstrated that the T cell marker OKT4 identifies T cell sets containing helper cells, whereas OKT8 reacts with the suppressor and cytotoxic T cell effectors. More detailed analysis of the OKT4+ subset, however, demonstrated that there is functional heterogeneity in the OKT4+ population. The evidence for this heterogeneity arose from studies on (1) the relative radiosensitivities of the distinct immunoregulatory functions of cells contained within this set, and, (2) the effects of the state of activation of this population on immune function. For example, OKT4+ cells included radiosensitive helper cells, radioresistant helper cells, and radiosensitive inducers of suppressor cells. Furthermore, after activation, the OKT4+ population also contained cells capable of suppressing B cell differentiation. Since activation of the OKT4+ population results in the emergence of cells with counterbalancing immunoregulatory properties, it was of interest to determine whether the state of activation of the OKT8+ population influences the immunoregulatory potential of this subset. In the experiments reported here E+ cells were cultured with pokeweed mitogen (PWM) for 60-70 h and then thoroughly depleted of OKT4+ cells, leaving OKT8+ cells. The ability of the PWM-activated OKT8+ cells (first culture) to exert suppressive activity was determined by adding graded numbers of these cells to fresh autologous OKT4+ cells and B cells. The cell mixtures were cultured in the presence of PWM for 5 days and then assayed for plaque-forming-cell (PFC) activity by the reverse hemolytic plaque assay. Our studies demonstrate that activation of OKT8+ cells results in the emergence of cells with apparently counterbalancing immunoregulatory properties. Activated nonirradiated OKT8+ cells consistently suppressed B cell immunoglobulin production. However, the immunoregulatory function mediated by irradiated activated OKT8+ cells is highly dependent on the magnitude of the helper activity obtained with fresh OKT4+ cells. Thus, irradiated activated OKT8+ cells suppressed the generation of PFC only when the level of helper activity was optimal. However, when the level of help was not optimal, no suppressor activity was observed; rather, under these conditions, irradiated activated OKT8+ cells amplify the PFC response. We would emphasize that the amplification function of irradiated OKT8+ cells depends strictly on the presence of fresh OKT4+ cells. Irradiated activated OKT8+ cells alone are not helper cells, since addition of these cells to B cells thoroughly dep

Antibodies, Monoclonal↗
PubMed1984

The T4 surface antigen is involved in the induction of helper function.

The OKT4 monoclonal antibody reacts with a 62K m.w. glycoprotein present on a subset of human T cells with the capacity to help or induce B cell differentiation. The present studies were undertaken to determine whether the T4 molecule itself plays any role in the helper function mediated by T4+ cells. Using a series of monoclonal antibodies (OKT4, OKT4A-E), which react with distinct noncompeting epitopes of the T4 molecule, we found that OKT4A and OKT4E, but not OKT4, antibodies inhibited the induction of B cell differentiation by T4+ cells. This inhibition was apparent when using nonirradiated or irradiated T4+ cells, and was noted over a wide range of concentrations. Importantly, inhibition occurred only if the antibody was present during the first 24 hr of cell culture, and the presence of antibody did not alter the kinetics of induction of B cell differentiation. Thus, these data suggest that the T4 molecule plays an early, critical role in cellular interactions required for helper cell function.

Antibodies, Monoclonal↗
PubMed1984

Biologic functions of the OKT1 T cell surface antigen. I. The T1 molecule is involved in helper function.

The OKT1 (Leu-1) monoclonal antibody reacts with a 69 KD glycoprotein that is present on only a fraction of functionally mature thymocytes but is maintained on most peripheral T cells. In the study presented, we examined the role of this surface molecule in T cell function. We found that addition of the OKT1 antibody to B cells and autologous T4+ cells markedly enhances B cell differentiation. This enhancement was apparent when nonirradiated or irradiated T4+ cells but not T8+ cells were used. Moreover, the OKT1 antibody as well as the OKT1 F(ab')2 fragment enhanced B cell differentiation in a dose-dependent fashion. It is important to note that perturbation of the T1 molecule with OKT1 in the presence of autologous E- cells causes the rapid release of molecules that trigger B cells to proliferate and differentiate into Ig-secreting cells. These data when considered together suggest that OKT1 reacts with a T cell membrane determinant or a complex that is intimately involved in the execution of helper function on OKT4+ cells.

Antibodies, Monoclonal↗
PubMed1983

The immunologic and ultrastructural characterization of the cellular infiltrate in acute cardiac allograft rejection: prevalence of cells with the natural killer (NK) phenotype.

The inflammatory cell infiltrates in 15 endomyocardial biopsies serially obtained from a human cardiac allograft during a 1 1/2-year period were characterized. An indirect immunofluorescent technique with hybridoma-derived monoclonal antibodies which preferentially react with B lymphocytes (anti-Ia), mature T cells (OKT3, Leu 1), and helper (OKT4b,d) and supressor/cytotoxic (OKT8) T-cell subsets and with natural killer cells, macrophages, and granulocytes (OKM1) was used. During each of seven rejection episodes the overwhelming majority of infiltrating cells in the endomyocardial biopsy were OKM1+Ia. These cells displayed short microvilli, a moderate amount of cytoplasm, numerous mitochondria, a large amount of rough endoplasmic reticulum, Golgi, and an indented nucleus, that is, the ultrastructural features of large, granular lymphocytes. Thus, they morphologically and phenotypically resemble those lymphoid cells which have been shown to possess natural killer (NK) functions in man. Occasional Leu 1+OKT3+ cells, some of which were OKT8+, were also seen during acute rejection. In each instance following therapy and resolution of the rejection episode only rare OKM1+Ia- cells were present. At this time the majority of the cells were Leu 1+OKT3+OKT8+. Routine biopsies, performed at times without evidence of rejection, showed only reactivity for Ia antigens by the capillary endothelium. These studies demonstrate the prevalence of cells with the natural killer phenotype in this human cardiac allograft during episodes of acute graft rejection.

Acute Disease↗
PubMed1983

Relationship between human T cell functional heterogeneity and human T cell surface molecules.

Our knowledge of human T cell differentiation and function has expotentially increased during recent years. With this growth in knowledge there has been an increase in our appreciation of the complexity of the T-T interactions which initiate and control immune responses. A great deal remains to be learned concerning the mechanisms of these complex cellular interactions. In particular, it will be important to precisely understand the clear heterogeneity of functions within isolated subsets of OKT4+ and OKT8+ T cells. Perhaps, as importantly, it will be necessary to define more clearly the functions of the T4 and T8 molecules as well as the precise function of the other defined glycoproteins on the T cell surface. The evidence is clearly emerging that many of those molecules are not solely markers of unique functional subsets and are intimately involved in the functions of T cells.

Animals↗
PubMed1983

Functional subsets of human monocytes defined by monoclonal antibodies: a distinct subset of monocytes contains the cells capable of inducing the autologous mixed lymphocyte culture.

The induction of most immune responses requires the close cooperation between T cells and antigen-presenting cells (APC), presumably of monocyte/macrophage (M phi) lineage. To characterize human APC further, we used two monoclonal antibodies, OKM1 and OKM5, to isolate and identify M phi subsets. OKM1 has been described and recognizes cell surface antigens on most M phi and granulocytes. OKM5 recognizes cell surface determinants present on the majority of human M phi but does not recognize other hematopoietic cell types. A small subset of peripheral blood M phi is OKM1-OKM5+. Human peripheral blood E- cells were separated into OKM1+ and OKM1- subsets by a rosetting technique utilizing anti-Ig-coated red cells. The capacity to present self antigens in the autologous mixed lymphocyte culture (AMLC) resided predominantly within the E-OKM1- subset, even if surface membrane Ig-positive cells were eliminated. Similar experiments showed that the ability to stimulate in AMLC was contained in the E-OKM5+ population and in fact resided primarily within the E-OKM1-OKM5+ subset. All of these subsets were able to trigger allogeneic T cells to proliferate. The capacity of these APC subsets to present soluble antigens (mumps, tetanus toxoid) was also examined. The data demonstrated that although the majority of these APC are E-OKM1+, E-OKM1-OKM5+ cells can also present foreign antigen. Taken together, these data suggest OKM1 and OKM5 can be used to isolate two functionally distinct human M phi subsets. One subset (E-OKM1+) is capable of presenting soluble antigens but shows minimal ability to trigger AMLC. The other subset (E-OKM1-OKM5+) can also present soluble antigens but is the predominant subset that can trigger AMLC.

Animals↗
PubMed1983

Biological functions of T-cell surface glycoproteins.

The OKT4 monoclonal antibody reacts with a 62 KD cell surface glycoprotein present on a subset of human T cells with the capacity to help or induce B-cell differentiation. The OKT8 monoclonal antibody reacts with a 76 KD cell surface glycoprotein present on a subset of human T cells with the capacity to suppress B-cell differentiation. The current studies were undertaken to determine whether the T4 and/or T8 antigens themselves play any role in the helper or suppressor function mediated by OKT4+ or OKT8+ cells. Specifically, we asked if monoclonal antibodies that react with noncompeting epitopes on the T4 or T8 molecules could block helper or suppressor function. Isolated human B cells were triggered in vitro to differentiate into antibody-forming cells (AFC) by autologous OKT4+ cells and macrophages in the presence or absence of OKT4 antibodies. By means of a reverse hemolytic plaque assay, AFC were detected as plaque-forming cells (PFC). We found that OKT4A, but not OKT4, antibody inhibited the PFC response over a wide range of concentrations. The antibodies OKT4B, OKT4C, OKT4D, OKT4E inhibited the PFC response to varying degrees. Importantly, inhibition by OKT4A occurred only if the antibody was present during the first 24 hours of cell culture. In the second set of experiments, OKT8+ cells were added to cultures containing B cells, and OKT4+ cells in the presence or absence of OKT8 antibodies, PFC activity was measured 7 days later. We found that the addition of OKT8E or OKT8G, but not OKT8B, OKT8C, OKT8D, OKT8F, or OKT8H, antibodies significantly inhibits the suppressor function mediated by OKT8+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1982

Phenotypic heterogeneity of human T-cell malignancies: demonstration by monoclonal antibodies and cytochemical markers.

The present study sought to delineate the phenotypic heterogeneity of the human T-cell malignancies. Twenty T-cell neoplasms were investigated for reactivity with the OKT hybridoma monoclonal antibodies and expression of acid alpha-naphthyl acetate esterase (ANAE), beta-glucuronidase (BG), and acid phosphatase (AP) activity. Twelve cases (Mycosis fungoides, Sezary syndrome, cutaneous T-cell lymphoma, chronic lymphocytic leukemia) were OKT3'T4', ie, expressed the phenotype commonly associated with mature T-helper cells. These cases were further divisible into ANAE+BG+ (6 cases), ANAE-BG+ (5 cases), and ANAE-BG- (1 case) phenotypes. In contrast to the 12 OKT3+T4+ cases, the remaining 8 cases showed considerable inter- and intratumor heterogeneity with respect to reactivity with the OKT antibodies. Six of these cases (acute lymphoblastic leukemia, lymphoblastic lymphoma) expressed phenotypes consistent with various intrathymic stages of T-cell differentiation. Five of the latter 6 cases were AP+BG+ANAE-, analogous to the majority of normal cortical thymocytes; an OKT3+T4-T8+T10+ neoplasm was ANAE+, analogous to normal medullary thymocytes. Two cases expressed the previously undescribed OKT3+T4-T8-T10+ phenotype. These studies demonstrate that the T-cell malignancies are divisible into phenotypes which correspond to normal maturational stages of T-cell differentiation and functionally distinct T-cell subsets. Phenotypic analysis of the human T-cell malignancies may provide a basis for understanding their biological heterogeneity and may aid in the identification of transitional stages of T-cell differentiation and minor T-cell subsets.

Adolescent↗
PubMed1982

Further dissection of the functional heterogeneity within the OKT4+ and OKT8+ human T cell subsets.

Previous studies have suggested functional heterogeneity within the OKT4+ and the OKT8+ populations. For example, after activation the OKT4+ population contains not only helper cells but also cells capable of suppressing B cell differentiation. Previous studies also indicate that the reciprocal T cell population, OKT8+, does not provide helper activity but contains cytotoxic effector cells and radiosensitive cells important in the suppression of B cell differentiation. Using a new differentiation antigen, OKT17, which recognizes a surface antigen present on the majority of resting normal peripheral T lymphocytes but is present only on a subset of OKT4+ cells after activation, evidence was obtained that two functionally mature subsets can be distinguished within the OKT4+ population itself: OKT4+17+ radiosensitive suppressor cells and OKT4+17- radiosensitive helper cells. Recently, another monoclonal antibody, OKT20, has been described which is present on a small percentage of resting lymphocytes but is expressed in varying proportions on activated T cells. Functional analysis of normal resting human T lymphocytes demonstrated that the OKT20-depleted T cell subset was able to generate cytotoxic cells and to suppress antibody production to the same extent as did OKT8+ cells. On the other hand, when unselected T lymphocytes were cultured for six days in a mixed lymphocyte reaction and then depleted of OKT20 reactive cells, the cytotoxic effector T cells were eliminated. In contrast, OKT20-depleted T cells after identical activation were still able to suppress antibody production. These data provide evidence that following activation of OKT8+ cells, the OKT20 differentiation antigen becomes selectively expressed on cytotoxic effectors but not on suppressor cells.

Antibodies, Monoclonal↗
PubMed1982

Characterization of the alloactivated E+Ia+ cell capable of stimulating in mixed lymphocyte culture.

Human peripheral blood E+ lymphocytes were alloactivated by E- cells and then purified by repeat E+ selection. As described by others, alloactivated cells (E+d6) but not unactivated E+ cells were capable of stimulating both allogeneic and autologous mixed lymphocyte cultures (MLC). To further characterize the subset of cells responsible for this function, we used a variety of monoclonal antibodies to human T cells and monocytes. Treatment of E+d6 cells with anti-Ia OKI1) plus complement (C) abrogated their stimulating capacity. In contrast, treatment with the anti-T cell antibodies OKT3, OKT11A, OKT4, OKT8 plus C or anti-macrophage antibody (OKM1) plus C failed to eliminate their MLC stimulatory capacintibodies to human T cells and monocytes. Treatment of E+d6 cells with anti-Ia OKI1) plus complement (C) abrogated their stimulating capacity. In contrast, treatment with the anti-T cell antibodies OKT3, OKT11A, OKT4, OKT8 plus C or anti-macrophage antibody (OKM1) plus C failed to eliminate their MLC stimulatory capacintibodies to human T cells and monocytes. Treatment of E+d6 cells with anti-Ia OKI1) plus complement (C) abrogated their stimulating capacity. In contrast, treatment with the anti-T cell antibodies OKT3, OKT11A, OKT4, OKT8 plus C or anti-macrophage antibody (OKM1) plus C failed to eliminate their MLC stimulatory capacity. Because OKT3 recognizes the majority of T cells and OKT11A recognizes virtually all E+ cells, we reasoned that a contaminating non-T cell containing the MLC-stimulating capacity may be present within the alloactivated E+ population. To further address this question, E+d6 cells were positively and negatively selected using a rosetting technique with anti-Ig-coated red cells. The positively selected OKT3, OKT11A, OKT4, or OKT8 E+d6 cells retained minimal ability to stimulate MLC, whereas the corresponding negatively selected populations were highly enriched in this function. Phenotypic analysis of the isolated populations failed to demonstrate greater than 1% surface membrane Ig(SmIg) positive cells. Taken together, these results suggest that the MLC stimulatory capacity of alloactivated E+ cells is contained within an Ia+, OKM1-, SmIg- non-T cell subset.

Antibodies, Monoclonal↗
PubMed1982

Functional analysis of human T cell subsets defined by monoclonal antibodies. V. Suppressor cells within the activated OKT4+ population belong to a distinct subset.

In the present report, we characterize a monoclonal antibody directed at a surface differentiation antigen on human T cells. The monoclonal antibody, OKT17, recognizes a cell surface antigen present on the majority of resting normal peripheral T cells. In contrast, OKT17 is unreactive with normal B cells, B cell lines, T cell lines, or SIg+ CLL. Interestingly, after activation, the antigen recognized by OKT17 is lost from a subset of OKT4+ cells. We took advantage of this finding to explore further the functional heterogeneity within activated OKT4+ cells. Evidence was obtained that the PWM-activated OKT4+ subset remaining after depletion of OKT17-reactive T cells (OKT4+ 17-) contains radiosensitive helperr cells but is devoid of suppressor cells. In contrast, the activated OKT4+ 17+ population contains potent radiosensitive suppressor cells as well as radioresistant helpe cells. Taken together, these studies suggest that the OKT17 monoclonal antibody can differentiate two functionally mature, activated OKT4+ human T cells: OKT4+ OKT17+ radiosensitive suppressor cells and OKT4+ 17- radiosensitive helper cells.

Antibodies, Monoclonal↗
PubMed1981

Generation of functional human T cell hybrids.

Human T cell hybrids were generated by fusing lectin-activated normal and leukemic human T cells with an aminopterin-sensitive human T cell line. This mutant cell line, designated CEM-T15, was derived from the human T cell line CEM after chemical mutagenesis with ethane methylsulfonate and subsequent culture in medium containing 6-thioguanine. After polyethylene glycol-induced fusion, the cells were cultured in hypoxanthine-aminopterin-thymidine selective medium. More than 5 wk after fusion, evidence for successful hybridization was obtained by three independent criteria: (a) The majority of the cultures contained cells expressing the OKT3 surface antigen: this antigen is expressed on normal T cells but not on CEM-T15 cells. (b) Most of the cultures contained polyploid cells. (c) Some of the cultures provided helper activity in the generation of antibody-forming cells. This functional activity is absent from the CEM-T15 parental cell line. Evidence for functional stability of the hybrids greater than 20 wk after fusion was provided by several clones that not only continue growing exponentially but also maintain expression of OKT3 surface antigen and high levels of helper function. These T cell hybrids constructed using antigen-specific human T cells should be of considerable importance in further studies of the immunobiology of human T cells.

Aminopterin↗