CD45RA and CD45RO positive CD4 cells in human peripheral blood and periodontal disease tissue before and after stimulation with periodontopathic bacteria

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Abstract
Flow cytometric analysis was used to examine naive and primed or memory CD4 cells extracted from periodontal lesions compared with cells from peripheral blood of healthy subjects before and after stimulation with the periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. In peripheral blood, approximately 60% and 40% of CD4 cells were CD45RO+ and CD45RA+ respectively at day 0. Phytohaemagglutinin (PHA) induced CD45RO expression on almost 100% of CD4 cells. However, P. gingivalis and F. nucleatum stimulation did not cause any significant change in percentage of CD45RO+ CD4 cells except for a loss of antigen at day 6 together with re‐expression at day 7, which also occurred on cells cultured in medium only. CD45RA expression on PHA and bacterial‐stimulated peripheral blood CD4 cells remained fairly stable for the 10‐d culture period. Greater than 90% CD4 cells extracted from healthy or marginal gingivitis (H/MG) and adult periodontitis (AP) lesions were CD45RO+ and this was maintained on AP cells throughout the 6‐d culture period, except for a small decrease in the percentage of positive cells induced by P. gingivalis at day 3. Approximately 9% CD4 cells from H/MG tissue were CD45RA+, but about 22% AP cells expressed this antigen, and this increased again in P. gingivalis‐ and F. nucleatum‐stimulated cultures after 3 d. Therefore, in peripheral blood P. gingivalis and F. nucleatum do not act as nonspecific T‐cell mitogens and, in AP cells, these bacteria induce changes in phenotype, supporting previous data that although they may be polyclonal B‐cell activators, they activate antigen specific T‐cells.