Autoimmune destruction of beta-cells in nonobese diabetic (NOD) mice is greatly accelerated by adoptive cotransfer of syngeneic CD4+ and CD8+ T-cells from diabetic animals into newborn NOD mice. We followed, by in situ hybridization, the appearance of mRNA of the tumor necrosis factor (TNF)-alpha gene and, as a marker for activated cytotoxic T-cells, of the serine protease granzyme A gene in the cellular infiltrates generated by cell transfer at birth. Cells expressing the genes for granzyme A or TNF-alpha were seen in considerable numbers already on day 14, after adoptive transfer. These numbers gradually increased in the intra-islet infiltrates from day 14 through day 30 after adoptive transfer. Compared with our previous findings in NOD mice developing spontaneous insulin-dependent diabetes mellitus (IDDM) (Held W, MacDonald HR, Weissman IL, Hess MW, Mueller C: Genes encoding tumor necrosis factor alpha and granzyme A are expressed during development of autoimmune diabetes. Proc Natl Acad Sci USA 87:2239-2243, 1990), frequencies of cells with TNF-alpha and granzyme A mRNA were 2- and 12-fold higher, respectively, in transferred IDDM (trIDDM). TNF-alpha mRNA positive cells were predominantly found in the CD4+ T-cell subset of the pancreas-infiltrating cells, whereas granzyme A mRNA positive cells were mainly observed in the CD4- T-cell subset. The effects of the observed enhanced TNF expression upon the pathogenesis of trIDDM are as yet unknown.(ABSTRACT TRUNCATED AT 250 WORDS)