Tissue distribution of immunoglobulin-secreting cells in normal and IgA-deficient chickens.

A reverse hemolytic plaque assay was employed to enumerate lymphoid cells actively secreting either immunoglobulin (Ig)G, IgA, or IgM in the small intestine, lungs, and lymphoid organs of normal and IgA-deficient chickens. In normal birds, intestinal lamina propria lymphocytes were proportionately richest in cells secreting IgG and IgA whereas the bone marrow was richest in IgM-secreting cells. The highest ratio of IgA to IgG secreting cells was also found in the lamina propria lymphocytes of the intestine (0.9), followed by the IgA to IgG ratios in the intestinal epithelium (0.31), and the lungs (0.19). The IgA to IgG ratios in the bone marrow (0.08) and the spleen (0.02) were considerably lower. Thus, both the intestine and the lungs were relatively enriched in cells actively secreting IgA. These IgA-secreting cells are the likely source of the IgA found in such quantities in intestinal and respiratory secretions. The tissue distribution of Ig-secreting cells was also studied in two generations of birds with experimentally induced IgA deficiency. There was a striking diminution of IgA-secreting cells in all tissues, including the intestine and lungs, whereas cells secreting IgG and IgM were normal or increased. The lack of IgA-secreting cells in these birds represents the effects of donor suppressor T cells having specificity for IgA.