Detection of guinea pig T mu and T gamma cells by a double rosette assay

Lymphocytes expressing Fc gamma receptors suppress antigen-induced proliferation in cells from guinea pigs infected with virulent Mycobacterium tuberculosis

The immunomodulatory role of T lymphocytes expressing receptors for the Fc portion of IgG (T gamma cells) in BCG-vaccinated guinea pigs following pulmonary infection with a low dose of virulent Mycobacterium tuberculosis H37Rv was studied. Compared to uninfected animals, guinea pigs infected 2 or 4 weeks previously harbored significantly increased percentages of T gamma cells in the peripheral blood (twofold increase) and the spleen (50% increase), and at 4 weeks had nearly fourfold increases in T gamma cells in bronchotracheal lymph nodes draining the infected lungs. Removal of T gamma cells by panning on plastic dishes coated with a monoclonal antibody specific for guinea pig Fc gamma R resulted in significant increases in proliferative responses of splenocytes to Con A and PPD in vitro. Removal of T gamma cells from peripheral blood lymphocytes resulted in significantly increased responses to PPD and to recombinant mycobacterial hsp 65 and hsp 70 antigens. The isolated T gamma cells themselves did not proliferate when stimulated with Con A, PPD, or either of the specific mycobacterial antigens, even in the presence of syngeneic accessory cells. These results suggest that FcR gamma-bearing T cells may play an important immunomodulatory role in pulmonary tuberculosis, principally by suppressing antigen-induced proliferation in the rest of the lymphocyte population.

Protein malnutrition alters the distribution of Fc gamma R+ (T gamma) and Fc mu R+ (T mu) T lymphocytes in experimental pulmonary tuberculosis

Inbred, strain 2 guinea pigs were given isocaloric diets containing either 30% (control diet) or 10% (low-protein diet) ovalbumin and infected 4 weeks later by the respiratory route with virulent Mycobacterium tuberculosis. By using an Fc receptor rosette assay, the proportions of T lymphocytes bearing Fc receptors for immunoglobulin G (T gamma cells) or immunoglobulin M (T mu cells) were quantified in blood and lymphoid tissues taken postinfection. A significant elevation in the proportion of the putative suppressor T subset (T gamma) in the blood of protein-deprived guinea pigs was observed at all intervals postinfection. Conversely, the levels of the putative helper T subset (T mu) in the bronchotracheal lymph nodes draining the site of virulent infection in malnourished animals were significantly reduced. Diet did not influence T gamma or T mu cells in the spleens. Diet-induced loss of purified protein derivative-specific T-cell functions in tuberculosis may be associated with alterations in the proportions of or the balances between T gamma and T mu subsets.

Vaccination with Mycobacterium bovis BCG affects the distribution of Fc receptor-bearing T lymphocytes in experimental pulmonary tuberculosis

Inbred strain 2 guinea pigs were vaccinated with Mycobacterium bovis BCG or were left unvaccinated and challenged 6 weeks later by the respiratory route with virulent Mycobacterium tuberculosis. By using a double rosette assay with isotype-specific antibody-coated ox and uncoated rabbit erythrocytes, the proportions of T lymphocytes bearing Fc receptors for immunoglobulin G (IgG) (T gamma cells) or IgM (T mu cells) were quantified in tissues taken from animals that were killed within 4 weeks postchallenge. Tuberculin reactivity in vivo and in vitro and antimycobacterial resistance were also measured. BCG vaccination protected the guinea pigs and resulted in significantly enhanced proportions of T mu cells in the blood during the first 3 weeks and in the spleen during weeks 2 and 3 postchallenge. Levels of T gamma cells declined in all tissues during the first 3 weeks of infection and were unaffected by prior vaccination with BCG. Increased proportions of T mu cells in the blood were accompanied by dramatic tuberculin skin reactions and purified protein derivative-induced lymphoproliferation in BCG-vaccinated guinea pigs during the first 2 weeks following virulent pulmonary challenge. Peak levels of T mu cells in the spleens of vaccinated animals at 2 weeks coincided with the first appearance of virulent mycobacteria in that organ. BCG vaccination appears to influence immunoregulatory events in pulmonary tuberculosis through effects on the distribution of IgM Fc receptor-bearing (T mu cell) T lymphocytes.

Formation of IgM-binding factors by murine thymocytes

Normal mouse thymocytes activated with concanavalin A (Con A) released soluble factors which selectively inhibited rosette formation between human peripheral blood lymphocytes (PBL) and ox erythrocytes (Eo) sensitized with rabbit IgM antibodies. The factors were removed by absorption with mouse IgM-coupled Sepharose, and were recovered from the beads by elution at acid pH. They neither bound to mouse IgG-Sepharose nor inhibited rosette formation of PBL with Eo sensitized with rabbit IgG antibodies. Mouse IgM enhanced the formation of IgM-binding factors by Con A-activated thymocytes. Unstimulated normal mouse thymocytes also released IgM-binding factors upon incubation with mouse IgM. The molecular weights of IgM-binding factors were approximately 90-110 and 35-50 kDa as estimated by gel filtration. Each species of IgM-binding factors markedly suppressed the IgM-plaque-forming cell (PFC) response of sheep red blood cell-primed spleen cells and slightly suppressed the IgG PFC response.

Mediation of macrophage reactions in immune tissue injury

The chemotactic specificity of three types of macrophage chemotactic factors (MCF) -a, -b, and -c, from delayed hypersensitivity reaction (DHR) skin sites in guinea pigs, was analysed. MCF-c shared common antigenicity with the macrophage chemotactic lymphokine released from bovine gamma globulin (BGG) and horse radish peroxidase (HRPO) -stimulated lymphocytes, using an immunoadsorbent column conjugated with anti-MCF-c antibody. These purified lymphokines were very similar, or possibly identical in terms of physicochemical and serological properties. BCG-induced lymphokine seemed to exist as complexes with serum protein at the skin site. A change in the proportion of each MCF was observed during the development of DHR. Furthermore, MCF-a and -b attracted Ia- M1 cell line cells, while MCF-c attracted Ia+ cells. Moreover, the responsive guinea-pig monocytes were divided mainly into two distinctive migrating subpopulations. One subpopulation was responsive to MCF-a and -b, and the majority of responding cells were "Ia-negative". The second subpopulation was responsive to MCF-c and the predominant cell type was "Ia-positive". The data suggest that macrophage reactions in the DHR are mediated by MCF-a, -b, and -c and that MCF-c attracts Ia bearing accessory macrophages and MCF-a and b- attract Ia negative macrophages.

Fc receptor--more answers, more questions

Fc receptors, belonging to the most important surface structures of a number of cells participating in the immune processes, have been intensely studied during the past decade. The present review summarizes the contemporary knowledge of the specificity and heterogeneity of Fc receptors and of factors influencing their expression, and includes some views on their function. In addition, it mentions their relationship to other cell surface structures, expression of Fc receptors during ontogeny of the organism and in certain diseases. Finally, data concerning the isolation and biochemical characterization of the Fc receptor molecule are presented.

Chemotactic subpopulation of macrophage cell line cells (M1 cells) discerned by three macrophage chemotactic factors from delayed hypersensitivity reaction sites

The functional specificity of three types of macrophage chemotactic factors ( MCFs ), -a, -b, and -c, from purified protein derivative of tuberculin (PPD)-induced delayed hypersensitivity reaction (DHR) skin sites on guinea pigs, was analyzed using macrophage cell line cells, M1, established from myeloid leukemia cells of a SL/Am strain mouse. M1 cells yielded two subclones: Mk1 cells, which were Ia+ and migrated specifically toward MCF-c; and Mm1 cells, which were Ia- and migrated specifically toward MCF-a and -b. These differences show the heterogeneity of the biologic activities of the MCFs in the presence of cell line cells. M-1 cells, blast cells, when grown in continuous culture, migrated toward none of the MCFs . Upon differentiation to mature macrophage-like cells in conditioned medium (M+1 cells), however, they migrated to MCF-a, -b, and -c and the experimental evidence points to the possibility that M+1 cells are separated into subpopulations on the basis of their chemotactic response. Cytotoxic treatment of M+1 cells with anti-Ia antisera resulted in the specific decrease of activity toward MCF-c. Furthermore, MCF-c attracted Ia-positive M+1 cells, while MCF-a and -b attracted Ia-negative M+1 cells. Thus, our results indicate the existence of two migrating subpopulations of M+1 cells with specificities for MCF-a, and -b and for MCF-c, respectively. The data suggest that MCF-c attracts Ia-bearing accessory macrophages and MCF-a and -b attract Ia-negative macrophages in the DHR.