Lymphotoxin production by subsets of T cells.

Lymphotoxin is produced by T cells sensitized to antigen upon re-exposure in vitro. It is also elicited by mitogen treatment. Its production has been correlated with delayed-type hypersensitivity and it may be a mediator of that phenomenon. We have examined the Ly phenotype of the subset(s) of T cells that produce lymphotoxin in order to investigate the relationship of lymphotokin killing to allo-killing mediated by Ly2+ T cells. We have found that Ly1 T cells sensitized to ovalbumin secrete more lymphotoxin than Ly2 cells. The ovalbumin-sensitized T cells do not lyse their target in a short term 51Cr-release assay even when "glued" to the target with Con A. Thus, lymphotoxin-producing cells differ phenotypically from the previously defined cytotoxic T cells that bear the Ly2 differentiation marker.