Tonsillar (Waldyer's ring equivalent) lymphoid tissue in the rat: lymphocyte subset binding to high endothelial venules (HEV) and in situ distribution

Abstract

We have studied lymphocyte traffic to the Waldeyer's ring equivalent (WRE) lymphoid tissue of the rat, by measuring the in vitro binding of various lymphocyte subsets to high endothelial venules (HEV) in the WRE. In addition, we studied the in situ distribution of these lymphocyte subsets. WRE tissue consists of B and T cell areas; the latter contain HEV. B cells outnumber T cells, and T helper (CD4) cells outnumber T suppressor/cytotoxic (CD8) cells (T/B ratio = 0.7; CD4/CD8 ratio = 5.1). In vitro studies of lymphocyte binding showed that lymphocytes adhere almost equally well to HEV in WRE tissue as to HEV in lymph node (LN) tissue, and much better to HEV in WRE than to HEV in Peyer's patch (PP) tissue. T cells bind better than B cells to HEV in WRE (T/B binding ratio = 1.8), and CD8 cells better than CD4 cells (CD8/CD4 ratio of 2.9-3.2, dependent on cell source). The observed preference of T over B cells in binding to HEV is not reflecting the distribution of these lymphocyte sets in situ. In this respect the WRE takes a unique position, since in other lymphoid organs T/B binding ratios parallels T and B cell distribution in situ. This may suggest a much more rapid passage of T cells through the WRE than through other lymphoid tissues, although other mechanisms cannot be ruled out. The CD8/CD4 binding ratio to HEV in WRE contrasts with situ distribution of these cells also; however, this is found for LN and PP lymphoid tissue too.(ABSTRACT TRUNCATED AT 250 WORDS)