Influence of CD4-1+, CD4-2+ and CD8+ T lymphocytes subpopulations on the immune response of B lymphocytes in flounder (Paralichthys olivaceus) immunized with thymus-dependent or thymus-independent antigen.

In order to elucidate the influence of T lymphocytes subpopulations on B lymphocytes immune response, in this paper, CD4-1+, CD4-2+, CD8+ T lymphocytes and B lymphocytes responses to thymus-independent (TI) or thymus-dependent (TD) antigen plus immunosuppressant were investigated in flounder (Paralichthys olivaceus). The results showed that in LPS-immunized group, the percentages of CD4-1+, CD4-2+, CD8β+ T (PCD4-1+ T, PCD4-2+ T and PCD8β+ T) lymphocytes in peripheral blood leucocytes (PBLs) had no significant variations, the percentages of IgM+ B (PIgM+ B) lymphocytes and LPS-specific antibodies (LA) significantly increased and peaked at 3rd or 4th week post-injection; CsA had no inhibition on both T/B lymphocytes and LA; RaPa only suppressed the PIgM+ B lymphocytes and LA, and the inhibition maximum (Imax) were about 35% and 20%, respectively. In KLH-immunized group, the PCD4-1+, PCD4-2+ and PCD8β+ T lymphocytes significantly increased and peaked at 3rd or 5th day, successively the PIgM+ B lymphocytes and KLH-specific antibodies (KA) significantly increased to the peak at 5th week; the PCD4-1+, PCD4-2+ T and PIgM+ B lymphocytes and LA were inhibited significantly by both CsA and RaPa, and the Imax on them were 13%-33%, 11%-25%, 19%-34%, 22%-26%, respectively, while the PCD8β+ T lymphocytes showed no significant suppression. The results indicated that the suppression of PIgM+ B lymphocytes in KLH + CsA group was not directly derived from CsA, but due to the suppression of T lymphocytes, especially CD4+ T lymphocytes subpopulations. The results showed for the first time that, similar to higher vertebrates, T lymphocytes didn't respond to TI antigen, moreover, T lymphocyte subpopulations had a regulation on the immune response of B lymphocyte for TD antigen in flounder.