Biomedical subjects

N Khansari

Publications and source records attributed to N Khansari.

24 records · Page 2Linked to original sources

PubMed1983

Phagocytosis of senescent erythrocytes by autologous monocytes: requirement of membrane-specific autologous IgG for immune elimination of aging red blood cells.

The role of membrane-bound IgG present on the membrane of senescent erythrocytes in immune eliminations of aging red cells was investigated. Phagocytosis of populations of red blood cells (RBC) of different ages by autologous monocytes was assessed both by direct phagocytosis and by induction of microsomal heme oxygenase. Removal of IgG from older RBCs inhibited their phagocytosis; in contrast, preincubation of neuraminidase-treated young or in vitro aged RBCs with IgG eluted from old cells led to phagocytosis of RBCs treated by autologous monocytes. It was also found that the Fc portion of membrane-bound IgG is essential for the elimination of senescent cells; less than 15% of old heat-inactivated RBCs coated with F(ab)2 fragment of membrane-bound IgG were phagocytosed. In contrast, more than 50% of old heat-inactivated RBCs coated with heat-eluted IgG were phagocytosed by autologous monocytes. A possible mechanism of elimination of aged cells is discussed.

Adult↗

PubMed1983

Mechanisms for the removal of senescent human erythrocytes from circulation: specificity of the membrane-bound immunoglobulin G.

Direct antiglobulin (Coombs') tests of erythrocyte (RBC) subpopulations confirmed the presence of membrane-bound immunoglobulin G (IgG) on old (density greater than 1.110) human RBCs but not on the young (density less than 1.110) RBCs. After thermal elution of the bound IgG, this Coombs' reaction was negative, but incubation of thermally eluted IgG (He-IgG) with heat-treated RBCs induced a positive antiglobulin test. A positive direct antiglobulin reaction was also obtained after incubation of heat-treated RBCs with anti-T antibody. Similar results were obtained when young RBCs treated with Vibrio cholerae neuraminidase (VCN) were incubated with anti-T or with IgG eluted by heat from old RBCs. Nevertheless, pre-absorption of heat-eluted IgG with T and/or Tn antigen, did not prevent it from binding to either heat-treated old or VCN-treated young RBCs as assessed by the antiglobulin consumption assay. Pre-treatment of either VCN-treated young or heat-treated old RBCs with anti-T and/or anti-Tn antibodies had no significant effect on the binding of radiolabeled He-IgG (eluted from old RBCs). The results indicate that even though desialylation of the erythrocyte membrane is required for binding of both anti-T-Tn and He-IgG, the specificity and consequently the RBC binding sites for He-IgG and anti-T seem to be different.

Antigens, Tumor-Associated, Carbohydrate↗

PubMed1983

In vitro humoral immune response of human peripheral blood lymphocytes to tetanus toxoid sepharose 4B.

The in vitro immune response of unfractionated human peripheral blood lymphocytes (PBL) from immune donors who had not been re-immunized with tetanus toxoid (TT) prior to donation was investigated. In this study we were able to stimulate PBL with tetanus toxoid coupled to Sepharose 4B (STT) for production of anti-tetanus toxoid antibody (Ab). Soluble tetanus toxoid or STT alone did not stimulate production of specific Ab. Pokeweed mitogen (PWM) and STT were required for optimal production of IgG and IgM antibodies specific to tetanus toxoid. Specific Ab responses were reduced in low and high concentrations of STT. Depletion of monocytes had no effect on either total IgG or specific IgG synthesis, but decreased the synthesis of both total and specific IgM. Depletion of E-rosette-forming cells decreased the production of specific Ab, suggesting T-dependency of the immune response to STT. Simultaneous production of total immunoglobulin and specific Ab by Sepharose 4B was negligible in the absence of PWM. In the presence of PWM, total immunoglobulin production was optimal, and specific anti-TT Ab production was undetectable. The specificity of the anti-TT Ab was studied by absorption of the culture supernates with an STT column which removed all measurable specific Ab.

Antibody Formation↗

PubMed1982

Diagnosis of histoplasmosis and blastomycosis by an antiglobulin hemagglutination test.

An antiglobulin hemagglutination test was developed for detection of antibody directed to Histoplasma capsulatum and Blastomyces dermatitidis. The substances responsible for spontaneous agglutination of erythrocytes were removed from histoplasmin and blastomycin by vacuum dialysis, and partial purification of the antigens by gel filtration chromatography on Sephadex G-150 allowed removal of additional nonantigenic material which competed with the antigens for binding on the erythrocyte surface. The test was sensitive enough to detect antibodies in sera which were negative by complement fixation, immunodiffusion, or both, but it failed to discriminate reliably between antibody directed to H capsulatum and antibody directed to B dermatitidis. Erythrocytes sensitized with partially purified blastomycin produced some false-positive reactions with normal canine sera; this was corrected by diluting the antigen before sensitization of the erythrocytes.

Animals↗

PubMed1981

Immunosuppression in murine malaria: a soluble immunosuppressive factor derived from Plasmodium berghei-infected blood.

Mice infected with Plasmodium berghei have a depressed immune response to a variety of antigens. We report the extraction, purification, and characterization of a soluble immunosuppressive substance derived from P. berghei-infected mouse blood. A crude extract, prepared by solubilization of infected erythrocytes in a Parr cell disruption bomb, reduced the anti-DNP PFC response of mice injected with the extract 1 day before immunization. Purification of the immunosuppressant was accomplished by precipitation with 50% saturated ammonium sulfate followed by chromatography on Sephadex G-150 in the presence of 6 M guanidine hydrochloride. The immunosuppressive activity was recovered in the last fraction eluted from the Sephadex G-150 column that contained low m.w. components. The activity was abrogated by trypsin digestion, but not by periodate oxidation. Volume for volume, the purified immunosuppressant had a 100-fold greater activity than the crude extract from which it was derived. It suppressed the response to the T-dependent antigens DNP-KLH and SRBC, but not to the T-independent antigen DNP-Ficoll.

Animals↗

PubMedDate not supplied

Immunological dysfunction in Alzheimer's disease.

Peripheral blood lymphocytes from Alzheimer's patients and apparently healthy elderly individuals were examined for interleukin-1 (IL-1) production. Our results indicate severely low production of IL-1 by patient's peripheral blood monocytes. The low production of IL-1 in vitro correlated with patients' symptoms and therapy with 1-acetamide,2-pyrrolidone (1a,2p). In addition to low IL-1 production, the number of autologous rosette forming cells (ARFC) was significantly decreased in all Alzheimer's patients whereas B-cell glucose metabolism was significantly higher than age-matched healthy individuals.

Aged↗