Estrogen in autoimmunity: expression of estrogen receptors in thymic and autoimmune T cells

To identify the targets of estrogen in immune system lymphocytes and to examine gender differences in autoimmunity.

RNA samples from purified lymphocyte subsets were analyzed for the presence of mRNA for estrogen receptor alpha and beta (ER alpha and ER beta). Groups of male, female, and testicular-feminized mice were compared for autoantibody production.

Autoimmune-prone lpr (Fas-deficient), testicular-feminized (Tfm, androgen receptor-deficient) and wild-type mice were studied.

Lymphocyte subsets were purified by fluorescence-activated cell sorting (FACS) and RNA was assessed for the presence of estrogen receptor sequences using specific oligonucleotide primers and the reverse transcription-polymerase chain reaction (RT-PCR). Spontaneous and induced antibody production in mice was determined by enzyme-linked immunosorbent assay (ELISA).

ER alpha was expressed in all lymphocyte subsets examined. ER beta was expressed at low levels in thymic CD4/CD8- T cells in wild-type mice and at high levels in the peripheral CD4-/CD8- T cells in lpr mice. Both spontaneous and induced autoantibody production was higher in female lpr mice than in male lpr mice.

The presence of ERs in lymphocytes indicates that estrogen may affect immune cells during their development and mature function. The selective expression of ER beta may help explain some of the physiological effects of estrogen and its pharmacologic analogues and may lead to means to direct estrogen analogues to such cells. Such effects may be explored in lpr mice, given the enhanced capacity of female lpr mice for autoantibody production.