Transgene-derived mRNA is detectable in spleen and thymus of transgenic NOD/LtWehi mice, but not of control littermates, by reverse transcription followed by PCR (RT/PCR) using either primers for H2-Eak and proinsulin or two proinsulin primers. Immunoreactive proinsulin is detectable in medium from cultured transgenic splenocytes only after 8 days' culture and at levels 10-2 - 10-3 times those of cultured islets or islet cells; levels are increased by culture with interferon gamma and tumor necrosis factor alpha.