Abstract
We investigated the expression of CD99 in 35 hyperplastic perigastric lymph
nodes, which were resected for gastric carcinoma or chronic peptic ulcer.
Essentially, all lymphocytes in lymph nodes expressed CD99, but there were two
populations with respect to the intensity of CD99 expression--CD99high and
CD99low cells. We showed CD99high cells were distributed in paracortical and
medullary cords by immunohistochemical study while germinal center cells were
CD99low. Using three-color flow cytometric analysis with CD3, CD4, CD8, CD19,
CD23, CD45RA, CD45RO, CD69, CD138, IgM, IgD, and IgG, most of CD99high cells
were shown to be activated/memory T cells. CD4+CD45RO+ T cells were the subset
revealing the highest intensity of CD99 expression while CD4+CD45RA+ T cells
were CD99low. Among B cells, IgG+ B cells revealed a higher level of CD99
molecules than IgM+ B cells. These results suggest that CD99 is one of
activation-related molecules which are upregulated in recently activated
lymphocytes.