Lymphocytosis in rats treated with polyacids.

Inoculation of rats i.v. with dextran sulfate or polymethacrylic acid causes lymphocytosis. Electron microscopy of sections of cervical lymph nodes in control rats showed active passage of small lymphocytes through the high endothelial cells (HEC) of the post-capillary venules. In treated rats there was no indication of such passage: the HEC were free of small lymphocytes; and in about 25% of the venules apparently stationary lymphocytes, lacking microvilli, were found appressed to the luminal walls of the HEC.