The entry of T and B lymphocytes into rat popliteal lymph nodes undergoing a graft-versus-host reaction

Intrinsic Differences in L-Selectin Expression Levels Affect T and B Lymphocyte Subset-Specific Recirculation Pathways

Lymphocyte migration into lymphoid organs is regulated by tissue-specific adhesion molecules such as L-selectin and the α4β7 integrin. Whether L-selectin also regulates lymphocyte subset-specific migration into specific lymphoid tissues was examined in this study by comparing the migration of CD4+ T cells, CD8+ T cells, and B cells from L-selectin-deficient and wild-type mice. T cells were the predominant lymphocyte subset entering PLN, MLN, Peyer’s patches, and spleen during short term (1-h) migration assays. However, both B cell and CD4+ and CD8+ T cell entries into PLN, MLN, and Peyer’s patches were dramatically impaired (73–98%) by loss of L-selectin. Lymphocyte expression of α4β7 integrin did not compensate for the loss of L-selectin, since both B and T cells predominantly migrated into the spleen in the absence of L-selectin. The more efficient migration of T cells into peripheral lymphoid tissues relative to that of B cells was partly explained by the finding that T cells expressed L-selectin at 50 to 100% higher levels than B cells. In addition, a 50% reduction in L-selectin expression by lymphocytes from hemizygous L-selectin+/− mice resulted in a 50 to 70% decrease in short term lymphocyte migration into peripheral lymphoid tissues relative to that of wild-type lymphocytes. Thus, the differential migration of T and B lymphocyte subsets to lymphoid tissues is regulated in part by subset-specific differences in L-selectin expression levels.

Lymphocyte homing

The phenomenon of "homing" is discussed with respect to patterns of lymphocyte circulation and the molecules on the surface of both endothelium and lymphocytes that mediate this process. In addition, the data are analysed in the context of a model for lymphocyte homing.

CD4+ lymphocytes are extracted from blood by peripheral lymph nodes at different rates from other T cell subsets and B cells

The circulation of lymphocyte subsets through prescapular lymph nodes in sheep has been quantified using a panel of monoclonal antibodies against sheep lymphocyte surface antigens. Differences in the extraction of lymphocyte subsets from blood by the lymph node were found with CD4+ lymphocytes being extracted at a faster rate (1/2) than CD8+, SBU-T19+, major histocompatibility complex class II+ and B cells (1/4 to 1/5). In order to accommodate existing data on organ-specific adhesion molecules, one subset specific and one tissue specific, expressed on vascular endothelium could act jointly to regulate the migration of recirculating lymphocytes.