Immunobiology of chicken germinal center: I. Changes in surface Ig class expression in the chicken splenic germinal center after antigenic stimulation.

The germinal center (GC) develops after antigenic stimulation and is thought to occur at the site of various immune responses. We separated a single GC from chicken spleen after antigenic stimulation. Flow cytometric analysis of the cells derived from a single GC and RT-PCR analysis of Ig mRNA expression in GC was performed. Direct evidence indicates that: (1) there was a considerable difference in the cell population of each GC, (2) the ratio of CD3+ cells in a GC remains constant at 10–20%, (3) the highest proportion of sIgY+ cells in a GC occurs 1 week after the time of highest proportion of sIgM+ cells, and (4) RT-PCR analysis was used to detect IgY mRNA expression in a GC. The continuous existence of CD3+ cells, the alterations in sIgM+ and sIgY+ cell ratios, and the expression of IgY mRNA strongly suggest that Ig class switching occurs in the GC during an immune response.