A system of alloantigens that selectively identifies lymph-node lymphocytes.

The antiserum (BALB.I-H-2j x SWR/J)F1 anti-I.29 ascites cells, in reaction with B6 lymph-node cells (LNC) in the cytotoxicity assay, defines an alloantigen system called Lna-1 (lymph-node alloantigen-l) which in normal, untreated mice is expressed on the cells of lymph nodes but not of other lymphoid organs. The T- and B-cell populations of lymph nodes evidently include Lna-1+ subpopulations representing 30-40 percent of the total population The Lna-+ phenotype could be induced on cells of thymus and spleen but not of bone marrow. Congenitally asplenic +/Dh mice have no Lna-1+ cells in their lymph nodes, but their LNC can be induced to express Lna-1; this suggests that the spleen is normally required for the differentiation of Lna-1+ cells from Lna-1- precursors. It is not yet known whether thymus is also required for the expression of Lna-1 in lymph nodes. It remains to be seen whether the existence of the Lna-1+ B-cell subpopulation of lymph nodes depends on Lna-1+ T cells, and whether the Lna-1+ phenotype of B cells may be acquired rather than intrinsic. One hypothesis which is the basis of further study is that there is a T-cell pathway in which noninducible bone-marrow cells become Lna-1-inducible in the thymus, then travel to the spleen, where they are induced to become Lna-1+, after which they reside in lymph nodes.