Bursectomized chicks received lymphocyte single cell suspensions harvested from the bursa of Fabricius (BF), ileal lymphoid aggregate (ILA), caecal tonsils (CT), spleen and peripheral blood. Four days after cell transfer, repopulation of the duodenal and CT lamina propria in age-matched recipient bursectomized chickens with IgA-secreting plasma cells was determined. The results indicate the highest level of reconstitution with cells derived from BF, but substantial numbers of IgA-secreting plasma cells were also observed in a number of birds that received lymphocytes originating from the ILA and CT.