The influence of antigenic stimulation on the ontegeny of lymphoid aggregates and immunoglobulin-containing cells in mouse bronchial and intestinal mucosa.

The requirement of Ag for the localization of precursors of IgA-producing cells in mucosal surfaces was tested in a model in which fetal tissues develop in an Ag-free adultA/J mice. At 30 days after transplantation primitive Peyer's patches )gut associated lymphoid tissue) and bronchus associated lymphoid tissue were seen in 1/3 of the animals examined and in all animals examined at 60 days. Immunoglobulin A-containing cells first appeared between 5 and 15 days in transplanted fetal guts. Their numbers increased to reach a plateau at 60 days at which time they approximated that of germ-free animals and were about 1/3 that of 60 day old normal mice. Immunoglobulin G and IgM containing cells were rarely seen, Few Ig-containing cells were present in fetal lungs. Fetal gut lumenal IgA sedimented in sucrose density gradients as if it were larger than serum IgA. Thus, in the absence of Ag, IgA plasma cells are present in mucosal tissues but their numbers are reduced.