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 control of the major histocompatibility complex (MHC) class I regulatory sequences show low level expression of IL-4 in all organs investigated. Several weeks after birth the animals develop thymus hypoplasia with a loss of CD4+CD8+ double-positive cells and a relative increase 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 affected. Many of the residual T cells exhibit the CD44highMel-14low phenotype of antigenically experienced T cells. B cells also show an activated phenotype with respect to size, MHC class II and CD23 expression, are more readily stimulated by anti-mu F(ab')2 antibodies than are B cells from control littermates, and show a higher spontaneous and antigen-induced production of IgG1 and IgE.