Expression of macrophage inflammatory protein-3α, stromal cell-derived factor-1, and B-cell-attracting chemokine-1 identifies the tonsil crypt as an attractive site for B cells

The expression of 3 lymphoid chemokines - macrophage inflammatory protein-3 alpha (MIP-3 alpha), stromal cell-derived factor-1 (SDF-1), and B-cell-attracting chemokine-1 (BCA-1) - in the tonsil and the possible correlation between their sites of expression and B-cell localization within this tissue were studied. The results show that all 3 chemokines are produced in the crypts but differ by the nature of the cells that produce them and their location within the crypt, SDF-1 and MIP-3 alpha are produced by epithelial cells, but their secretion is mutually exclusive. Both MIP-3 alpha- and SDF-1-expressing cells are in close contact with memory B cells. By contrast, BCA-l-producing cells in the crypt are not epithelial and form clusters colocalized with plasma cells, Altogether, these data suggest that the chemokines produced in the tonsillar crypt may (1) attract memory B cells to antigen and (2) recruit and retain plasma cells and memory B cells within the supportive epithelial microenvironment of the crypt.