Neonatal estrogen treatment and its consequences for thymus development, serum level of autoantibodies to cardiolipin, and the delayed-type hypersensitivity response.

Eight-week-old female and male NMRI mice treated neonatally with the synthetic estrogen diethylstilbestrol (DES), estradiol-17beta, or tamoxifen displayed an enlarged thymus when compared with controls (approximately 1.5-fold). In control females, either ovariectomy or adrenalectomy increased thymus weight to the level characteristic for DES-treated females, but these endocrine ablations had no significant effect in DES females. The serum estrogen levels were similar in intact DES, ovariectomized DES, and ovariectomized female controls; serum corticosterone was similar in controls and DES females. The expression of the Thy1.2+ marker and the percentages of CD4+CD8+ DP and CD4+ and CD8+ SP cell subsets were similar in thymocyte populations from 8-wk-old controls and DES females; the CD4+ and CD8+ SP subsets were similar in splenocyte populations. The levels of serum immunoglobulin (Ig) G and IgM autoantibodies to cardiolipin showed age-dependent fluctuations but were similar in controls and DES females; however, the IgG autoantibodies in DES females were qualitatively different from those in controls with respect to sensitivity to bovine serum (a source of beta2-glycoprotein I). Contrary to females, DES-treated males had higher levels of autoantibodies than controls. The delayed-type hypersensitivity (DTH) response to oxazolone was similar in controls and DES animals at 8 wk, increased in DES females and males at 6 mo, but was reduced in DES females at 1 yr. Thus, even though adult mice with thymus enlargement after neonatal estrogen treatment do not differ from controls with respect to the expression of the Thy1.2 marker or percentages of CD4+/CD8+ DP or SP subsets in thymus and spleen, qualitative and quantitative differences occur in immune parameters (autoantibodies to cardiolipin) and a T-cell-dependent immune response (DTH).