Loss of J chain during primary immune responses in chicks.

J chain positive cells (JPC) were studied by direct immunofluorescence in embryonic and newly hatched chicks. The results indicated a decrease in the amounts of JPC in the embryonic spleen and bursa of Fabricius after in ovo antigenic stimulation with sheep erythrocytes (SRBC) compared with that of unstimulated lymphocytes. The level of thymic JPC in the control chicks and those subjected to antigenic stimulation was always about the same. Partial re-expression of the J chain in splenic lymphocytes was detected in newly hatched, antibody producing chicks, while the percentage of JPC in non-antibody producing chicks did not recover to the control level. Further evidence obtained indicated that the JPC decreases did not depend on the antigen dosage. After antigenic stimulation, J chain re-expression in cells of embryos and newly hatched non-antibody producing chicks was found to be essentially the same. These findings imply that the re-expression of J chain molecules is associated with immunoglobulin production. Furthermore, it seems plausible that the non-re-expression of the J chain occurred at the time of immunological unresponsiveness.