Cytokine production of in vitro stimulated peripheral lymphocytes during the course of pregnancy and pseudopregnancy in the rat

Problem Does maternal lymphocyte cytokine production after in vitro stimulation vary with the stage of pregnancy in the rat? Method of study Blood samples were taken during the estrus cycle in rats (n = 11). Thereafter, rats were rendered pregnant (n = 6) or pseudopregnant (n = 5) and blood samples were taken at days 4, 8, 11, 15, and 20 of pregnancy and pseudopregnancy. White blood cell (WBC) count was measured and whole blood was stimulated with phorbol 12‐myristate 13‐acetate and calcium ionophore; interferon‐γ (IFNγ) and interleukin‐4 (IL‐4) production as well as (sub)populations of lymphocytes were measured using flow cytometry. Results We observed an increase of WBC in the second week of pregnancy and a slowly decreasing percentage of lymphocytes during the course of pregnancy. The percentage IFNγ producing T‐lymphocytes after in vitro stimulation was increased during pregnancy (for Th‐lymphocytes only in the second week of pregnancy, for Tc‐lymphocytes at all days). This increased IFNγ production in pregnant T‐lymphocytes was accompanied by an increase during pseudopregnancy, and therefore may result from increased sex hormone concentrations. The percentage IFNγ producing natural killer (NK) cells after in vitro stimulation was decreased on day 20 of pregnancy. No effect of pregnancy or pseudopregnancy was seen on percentage IL‐4 producing lymphocytes after in vitro stimulation. Conclusion In the rat the IFNγ production after in vitro stimulation varies during pregnancy and is increased, rather than decreased, during pregnancy.