The MiUe Lacs Band of Chippewa Indians in central Minnesota was screened for rheumatoid arthritis, with a 77% completion rate of the reservation census. Rheumatoid arthritis was found in marked excess, namely 6.8% of those evaluated or, minimally, 5.3% of the total band if all persons had been evaluated with no additional cases identified. This relatively closed population thus provides an opportunity to assess genetic and environmental factors of significance in this disease.

No abstract

The fate in culture of the T cell growth factor (TCGF), which is required for continued growth of human cultured T cells (CTC) in vitro, was studied. TCGF activity was stable for 7 days at 37°C. However, it was no longer detectable after incubation with actively growing CTC at 37°C for 3 days. This loss of TCGF activity also occurred quite rapidly and was detectable within 1 hr of incubation of 0.3 ml supernatant with 2 to 5 × 107 CTC at 23°C. 2 × 108 mononuclear peripheral blood leukocytes were not effective in removing TCGF activity, and incubation with similar numbers of cells from B and T cell lines had no effect. Three-day-old concanavalin A and phytohemagglutinin blasts were very reactive with TCGF, so that 107 or 2 × 107 cells consistently removed TCGF activity. These experiments suggested specific absorption of TCGF by activated T cells, and led us to develop a model of ligand-activated TCGF-induced proliferation of T cells: Ligands induce production of TCGF by T-producer cells and deliver a first signal to the T-responder cells. This causes a receptor for TCGF to appear on T-responder cells. Only then does TCGF deliver the obligatory second signal that is needed to drive the T-responder cells into proliferation.