Circulating immune complexes may be associated with increased suppressor T-cell activity in atopic allergy

The major circulating immunosuppressive activity in American visceral leishmaniasis patients is associated with a high-molecular weight fraction and is not mediated by IgG, IgG immune complexes or lipoproteins

Opportunistic infections, due to disease-related immunosuppression, constitute the major cause of death in American visceral leishmaniasis (AVL). Sera from these patients (AVL sera) non-specifically inhibit the in vitro proliferative response of normal human lymphocytes to lectins or antigens. In the present work, the mediation of this inhibition by IgG, immune complexes and low- or very low-density lipoproteins was studied. AVL serum fractions containing proteins with the molecular weight of IgG, and IgG, purified from AVL sera by anion exchange chromatography, did not suppress the lymphoproliferation. Most of the suppressive activity of AVL sera was associated with a fraction containing molecules with molecular weights above 430 kDa. This would be compatible with it being due to immune complexes and/or lipoproteins, and not to soluble IL-2 receptors as reported previously. However, neither of the two possibilities seem to be the case, as (1) depletion of immune complexes by protein-A followed by protein-G chromatographies did not affect the serum suppressive activity, (2) no correlation between immune complex contents and suppressive activities in individual sera was observed, and (3) plasma lipoproteins (VLDL and LDL), purified from AVL patients and from healthy individuals, had the same degree of immunosuppressive activity.

Serum-mediated suppression of lymphocyte transformation responses in coccidioidomycosis

Lymphocyte transformation (LT) responses to coccidioidin (CDN) and spherulin were suppressed in 11 (73%) of 15 patients with active coccidioidomycosis when their mononuclear cells were assayed in autologous serum as compared to serum from healthy, CDN skin test-positive subjects. Suppressed LT responses were specific for Coccidioides immitis antigens in 7 (64%) of the 11 patients. Immunoaffinity chromatography of patient sera with Staphylococcus protein A adsorbed the suppressor component(s) and thereby established that suppression was attributed to immunoglobulin G, either alone or complexed with antigen. The possibility that suppression was mediated by immune complexes was examined by adding complexes formed in vivo or in vitro to mononuclear cell cultures of healthy CDN-reactive persons before LT assays. Although complexes prepared in this manner were reactive in an enzyme-linked immunosorbent assay designed to detect Coccidioides antigen-specific immune complexes, no suppression of LT responses was observed. We conclude that serum-mediated suppression of LT responses in coccidioidomycosis is attributed to monomeric and not immune-complexed immunoglobulin G antibody.

Atopic asthma: T lymphocyte subpopulations

Atopy is associated with diminished cell-mediated immunity and increased amounts of IgE, both of which may be caused by imbalances of T lymphocyte subsets. We compared the composition of highly purified peripheral-blood T cells of fifteen atopic asthmatics with ten non-atopic control subjects. Each subject was examined on five separate occasions. Indirect immunofluorescence using monoclonal antibodies was used to define T cell subsets. We examined the proportion of T cells with T3 (most T cells), T4 (helper/inducer), T8 (suppressor/cytotoxic), M1 (natural killer), and Ia (activated T cells) surface antigens. Blood was obtained at the same time of day to eliminate the effects of circadian rhythm. Subjects were taking no medications. We found no difference between the groups of the percentage of T cells with T4, T8, M1, and Ia antigens, nor the ratio of T4+ (helper) to T8+ (suppressor) cells. T3 percent was slightly (94.3 vs 92.5%) higher in the atopic group. We conclude that atopic asthma is not associated with imbalances of peripheral-blood T cell subsets.

Atopic asthma: T-cell response to corticosteroids

Atopic asthma is associated with diminished cell-mediated immunity and elevated levels of IgE, both of which may be caused by imbalances of T-lymphocyte subsets. We analyzed the response of peripheral blood T-cell subsets to two commonly used corticosteroid preparations as a probe of T-cell subset regulation. We administered prednisone (P) 60 mg or 20 mg, beclomethasone dipropionate (BDP) aerosol, 336 micrograms, placebo, or BDP vehicle in a double-blind protocol to 15 atopic asthmatic patients and ten nonatopic subjects. No difference was found between the groups of the baseline number of T-cells with T4, T8, M1, and Ia antigens, nor the ratio of T4+ (helper) to T8+ (suppressor) cells. Five hours after administration of BDP aerosol, BDP vehicle, and oral placebo, there was no change of these values in either the atopic or in the nonatopic group. In contrast, P, 20 and 60 mg, caused a fall of T4/T8 ratio in the atopic, but not in the nonatopic population. Atopic asthma is not associated with baseline imbalances of peripheral blood T-cell subsets, but is associated with an abnormal response to systemic, but not inhaled corticosteroid.

Potentiation of the canine lymphocyte blastogenic response by indomethacin

Cultivation of normal canine peripheral blood lymphocytes in the presence of indomethacin, a potent prostaglandin synthetase inhibitor, produced a consistent potentiation of their in vitro response to mitogenic stimulation as compared to cultures without indomethacin. The enhancing effect of indomethacin increased with decreasing concentrations of mitogens. Indomethacin had to be added to the cultures during the first four hours for the potentiating effect to be observed. These data suggest that prostaglandins may play an important role in the regulation of the dog's immune response.