DIFFERENT PATTERNS OF TCR TRANSGENE EXPRESSION IN SINGLE-POSITIVE ANDDOUBLE-NEGATIVE T-CELLS - EVIDENCE FOR SEPARATE PATHWAYS OF T-CELL MATURATION

Two lines of transgenic mice were established using the TCR alpha(V al pha 4.4-J alpha 24)- and beta(V beta 9-D beta 1.1-J beta 2.1)-chain ge nes from a cloned CD4(-)CD8(-)alpha beta(+) (double-negative; DN) T ce ll line from BALB/c mice. The TCR genes were expressed in CD4(+)CD8(-) and CD4(-)CD8(+) (single-positive; SP) and double-positive (DE) T cel ls in the thymus, and in SP T cells in the peripheral lymphoid tissues , and marrow in one transgenic mouse line, and predominantly in DN T c ells in the other. Bone marrow precursor cells from only the DN mouse line generated T cells expressing the V beta 9 transgene during tissue culture. V beta 9(+) T cells were found in DN but not SP transgenic m ice backcrossed to BALB/c nu/nu mice. The results suggest two separate pathways of T cell maturation, one which generates SP T cells in the thymus, and another which generates DN T cells in both the thymus and bone marrow.