Association of T cells with proliferating cells in lymphoid follicles

Frozen sections of lymph nodes from normal mice were examined by immunofluorescence with anti-T lymphocyte and anti-Ig reagents and by autoradiography following [3H]TdR administration. The scattered T lymphocytes present among B lymphocytes of primary follicles were found to be mostly nonproliferating; the few proliferating cells in primary follicles are therefore predominantly B lymphocytes. More than one-half (56%) of these proliferating B lymphocytes were found to be in direct contact with a T lymphocyte; this incidence is 5-fold higher than that expected by random association. In germinal centers, virtually all proliferating cells were found to be non-T lymphocytes as well. The association of proliferating B cells with T cells may be the result of specific cooperation between these two cell types. These data are discussed in the context of what is known of T/B collaboration and of primary follicles as a possible site of this interaction.