Mononuclear Cell Clusters Observed in Pars Intermedius of Human Hypophysis
We observed cell clusters morphologically resembling lymphocytes in the pars intermedius of human hypophyses, and investigated their immunohistochemical properties. These morphologically lymphocyte-like cells were not immunostained by any of the antibodies to hormones known to be present in the adenohypophysis or antidody to S-100 protein. However, immunostaining using antibodies to T cell membrane and B cell membrane showed that the cells were mainly stained by anti-B cell membrane antibodies. To investigate the stage of maturity of these B cell membrane-positive cells, we performed immunostaining using antibodies to IgG, IgM and IgA, and obtained negative results for all three. However, the present study did not answer the questions of why these cells are found only in the pars intermedius, why they are mainly B cells, and what functions they possess. Although there is so far no evidence suggesting a relationship between this cell cluster and functions of the pars intermedius in the hypophysis, the pars intermedius in human is considered more degenerate compared to amphibians, birds and rodents, and is likely to possess some yet undiscovered functions.