Mouse lymph node germinal centers contain a selected subset of T cells--the helper phenotype.

Cells staining for Lyt-1 are more frequent than cells staining for Lyt-2 in both primary follicles and the cuffs of secondary follicles; there is an even more striking predominance of cells bearing only Lyt-1 in germinal centers. In addition, there is an increase in the total percentage of cells bearing T cell antigens in germinal centers compared to primary follicles. These differences in phenotype and distribution of T cell populations indicate the T cells in B cell areas, and especially in germinal centers, are not randomly selected, but rather represent a specific subpopulation of T cells enriched for the helper phenotype (Lyt-1+2-), perhaps involved in the development and/or function of germinal centers.