Distribution of immunoglobulin-containing cells in normal and neonatally thymectomized rats

The distribution of immunoglobulin-containing cells (ICC) of the immunoglobulin A (IgA), IgG, and IgM isotypes was examined in various lymphoid and secretory tissues of rats. The effect of neonatal thymectomy of rats on T cells, B cells, and ICC in these tissues was determined by immunofluorescence. The results showed that although T cells were severely depleted in both lymphoid and secretory tissues of the thymectomized (Tx) rats, Tx and normal rats showed comparable numbers of B cells staining for IgA, IgG, and IgM. After neonatal thymectomy, IgA ICC in both lymphoid and secretory tissues were significantly decreased. However, the Tx rats exhibited a compensatory increase in IgM ICC in the identical tissues. Local injection of normal and Tx rats with Streptococcus mutans 6715 resulted in an increase in all isotypes of ICC in the secretory tissues. Although the primary increase in normal rats was due to IgA ICC, Tx rats exhibited the greatest change in the number of IgM ICC.