T-CELL SUBSET DISTRIBUTION AND B-CELL HYPERREACTIVITY IN MICE EXPRESSING INTERLEUKIN-4 UNDER THE CONTROL OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I REGULATORY SEQUENCES

Transgenic mice in which interleukin-4 (IL-4) is expressed under the c ontrol of the major histocompatibility complex (MHC) class I regulator y sequences show low level expression of IL-4 in all organs investigat ed. Several weeks after birth the animals develop thymus hypoplasia wi th a loss of CD4(+)CD8(+) double-positive cells and a relative increas e in the mature population, especially, and in contrast to previously published lines, the CD4(+) single-positive cells. In the periphery, T lymphocytes eventually decline, CD8(+) cells being more strongly affe cted. Many of the residual T cells exhibit the CD44(high)Mel-14(low) p henotype of antigenically experienced T cells. B cells also show an ac tivated phenotype with respect to size, MHC class II and CD23 expressi on, are more readily stimulated by anti-mu F(ab')(2) antibodfies than are B cells from control littermates, and show a higher sontaneous and antigen-induced production of IgG1 and IgE.