High CD99 expression in memory T and B cells in reactive lymph nodes
1Department of Pathology, Sungkyunkwan University School of Medicine, Suwon, Korea.
Insights
CD99 is expressed on most lymphocytes in lymph nodes, with higher levels on activated/memory T cells and IgG+ B cells. This suggests CD99 is an activation-related molecule upregulated on recently activated lymphocytes.
Area of Science:
- Immunology
- Cell Biology
Background:
- CD99 is a cell surface glycoprotein involved in lymphocyte activation and T-cell receptor-mediated responses.
- Its expression patterns and role in differentiating lymphocyte subsets within human lymph nodes require further elucidation.
Purpose of the Study:
- To investigate the expression levels and distribution of CD99 on lymphocytes in hyperplastic perigastric lymph nodes.
- To determine the relationship between CD99 expression intensity and lymphocyte activation status.
Main Methods:
- Immunohistochemical analysis of CD99 expression in 35 hyperplastic perigastric lymph nodes.
- Three-color flow cytometric analysis using a panel of lymphocyte subset markers (CD3, CD4, CD8, CD19, CD23, CD45RA, CD45RO, CD69, CD138, IgM, IgD, IgG).
Main Results:
- All lymphocytes expressed CD99, with distinct CD99high and CD99low populations observed.
- CD99high cells were primarily located in paracortical and medullary cords, while CD99low cells were found in germinal centers.
- Flow cytometry identified CD99high cells as predominantly activated/memory T cells (CD4+CD45RO+), whereas CD4+CD45RA+ T cells were CD99low.
- Among B cells, IgG+ cells showed higher CD99 expression than IgM+ cells.
Conclusions:
- CD99 expression is heterogeneous among lymphocytes in hyperplastic lymph nodes.
- CD99 upregulation correlates with lymphocyte activation, particularly in memory T cells and IgG-expressing B cells.
- CD99 functions as a marker for recently activated lymphocytes.
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.
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