[Effects of thyroxine on IgM production and beta-adrenergic receptor on lymphocyte in mice]

The effects of thyroxine (L-T4) on the IgM production of splenocytes in mice induced by sheep red blood cell (SRBC) were investigated by means of spectrophotometry of quantitative hemolysis (QHS). The maximum binding site number (Bmax) and affinity (Kd) of beta-adrenergic receptors (beta-Adr. R.) on splenic lymphocytes of mice under the different thyroid functional status during immune response were determined by radio-ligand combination method. The IgM production and Bmax of beta- Adr. R. of splenic lymphocytes were increased in "hyperthyroid mice" and decreased in "hypothyroid mice" as compared with the control (P less than 0.01) during the 3rd to 5th day after immunization with SRBC, but affinity of beta-Adr. R. was not changed (P greater than 0.05). It is suggested that L-T4 could increase the IgM production in lymphocytes induced by SRBC in mice. The underlying mechanism seems to involve an increasing Bmax of beta-Adr. R. on the immune cell, thus enhancing its sensitivity to catecholamine.