Receptors for IgA on rabbit lymphocytes. I. Distribution, specificity, and modulation.

The distribution of IgA binding lymphoid cells in the rabbit was determined by using ox erythrocytes coated with specific secretory IgA. After overnight incubation at 37 degrees C, the average percentage of IgA binding lymphocytes detected in major IgA-producing organs (Peyer's patches, 14.4%; appendix, 8.4%; and mesenteric lymph nodes, 11.3%), was generally higher than that detected in systemic lymphoid tissue. Lymphocytes bearing receptors for IgA (RFc alpha) were detected immediately after isolation only in the spleen and failed to appear after overnight incubation only in the thymus. That these receptors were distinct from receptors for IgM or IgG was demonstrated by cross-blocking studies with purified IgG, IgM, and IgA immunoglobulins. RFc alpha were sensitive to pronase digestion at 1 mg/ml and were regenerated with overnight incubation. In preliminary studies designed to evaluate modulation of this receptor, it was found that a significant increase in the percentage of cells expressing RFc alpha could be induced by antibodies specific for rabbit immunoglobulin. This information as a whole is consistent with the premise that RFc alpha-expressing lymphocytes may be involved in the regulation or expression of IgA-mediated immunity.