Histological changes in rat bronchus-associated lymphoid tissue after administration of five different antigens.

Histological changes in bronchus-associated lymphoid tissue (BALT) following single intratracheal administration of five different antigens were studied in the rat. After administration of T-dependent antigens (i.e., horseradish peroxidase, bovine serum albumin, and Bacillus Calmette Guérin) only minor changes in BALT in the rat occurred. Intratracheal administration of a T-independent antigen (lipopolysaccharide) and a partly T-independent antigen (paratyphoid vaccine) resulted after 1 week in an increase in cytoplasmic IgM-containing (cIgM) blast cells and plasma cells; these appeared to enter via the high endothelial venules (HEV). After 6 weeks, germinal centers were seen.