The absolute numbers and percentages of peripheral T, B, and NK cells were assessed in 7 women, both during the second trimester of pregnancy and 6 months Postpartum. Furthermore, the in vitro responses of peripheral blood lymphocytes (PBL) to several mitogens and a preparation of Prevotella intermedia were compared in a period of experimentally‐induced gingivitis during pregnancy and post‐partum. Clinically, the periodontal pocket bleeding index (PPBI) was found to be higher during pregnancy than post‐partum. The absolute numbers of CD3, CD4, and CD19 positive cells appeared to be decreased during pregnancy as compared to post‐partum. However, the results did not indicate any evidence for a reduced in vitro PBL response to several mitogens and a preparation of P. intermedia during pregnancy. J Periodontol 1991; 62:663–667.

SUMMARYIn 219 HIV-1-infected men of the Amsterdam cohort we measured CD4 T cell numbers and in vitro T cell responses to CD3 MoAbs with or without CD28 costimulation and phytohaemagglutinin (PHA). The value of these markers was estimated for disease progression within 4 years. CD28 expression on T cells has been related to T cell responses. CD28 costimulation considerably enhanced T cell reactivity ( 8-10-fold) with lower coefficients of variation compared with reactivity to CD3 MoAb alone (median 5 versus 20). T cell reactivity to CD3 plus CD28 MoAb was decreased during HIV-1 infection and was besides CD4 T cell numbers the only independent predictor for progression to AIDS. Compared with the group with high CD4 T cell numbers the relative risk (RR) for the group with intermediate levels was 2 . 28, with low levels 5 . 20. In the groups with intermediate and low CD3 plus CD28 responses the RR was 2 . 04 and 4 . 16, respectively. The combined RR for both was 4 . 65 and 21 . 63. The independence of this marker was confirmed when the group with low CD4 T cell numbers was subdivided into groups with high, intermediate and low T cell responses. The expansion of CD8 CD28 ÿ T cells was already apparent in HIV ÿ homosexual men, but CD8 CD28 T cells specifically decreased in patients with AIDS. CD28 expression on T cells correlated moderately with T cell responses to CD3 plus CD28 MoAb. T cell reactivity to CD3 MoAb in the presence of CD28 MoAb is a stronger prognostic marker than T cell reactivity to CD3 MoAb alone.

The present study was designed to assess whether the in vitro stimulation of lymphocytes by sonicates of Bacteroides intermedius and Bacteroides (Porphyromonas) gingivalis is antigen specific or non‐specific. In addition, the role of T and B lymphocytes in these responses was assessed. Peripheral blood lymphocytes obtained from healthy volunteers were cultured in the presence of these bacterial preparations and the proliferative response was measured. In similar experiments the response of umbilical cord blood lymphocytes did not exceed background values. In limiting dilution experiments only 1:4000, 1:6800, and 1:8200 of the lymphocytes initially reacted to B. intermedius, which strongly argues for the antigen‐specificity of the response. Purified T cells, in the presence of monocytes, proliferated when stimulated with B. intermedius and B. gingivalis. As for B cell stimulation, the bacterial extracts were capable of inducing IgM production, which appeared to be T cell dependent. These findings support the notion that B. intermedius and B. gingivalis induce specific T cell activation; secondarily, a T cell dependent, polyclonal B cell activation may occur. J Periodontol 1990; 61:217– 223.

Experiments were performed to develop a lymphocyte culture system in which microtiter plates could be used as a practical and time‐saving technique. The suitability of different types of microtiter plates was tested, analyzing lymphocyte reactivity by means of thymidine incorporation after stimulation by PHA and in the MLG. Furthermore, it became clear that in this system the number of lymphocytes required per culture could be diminished. According to a Workshop program (this issue), some experiments were carried out to further clarify the reproducibility and reliability of this culture system.