SummaryOral administration of a protein antigen generates a serum factor that induces tolerance when transferred into naïve recipients. This serum factor has been described in rats as consisting of exosome-like structures or tolerosomes, which express major histocompatibility complex class II molecules (MHCII) and mediate antigen-specific tolerance. In this study, we investigated the functions of serum-derived tolerosomes both in vivo and in vitro. Tolerosomes were purified from the 100 000 g pellet fraction of serum from ovalbumin (OVA)-fed mice. When transferred into naïve recipient mice, the tolerosomes mediated OVA-specific tolerance. We also found that tolerosomes from OVA-fed mice induced the activation of OVA-specific T cells both in vivo and in vitro. The inoculation of severe combined immunodeficiency (SCID) mice with an interferon-c-producing cell line normalized the expression of MHCII in the intestinal epithelial cells and restored their ability to generate tolerosomes. Syngeneic but not allogeneic transfer of tolerosomes from OVA-fed donors induced tolerance in the recipients. Our results show that tolerosomes can be isolated from mouse serum, that tolerosome-induced oral tolerance requires MHCII expression in intestinal epithelial cells, and that tolerosomes are functional only in syngeneic recipients.

No abstract

Oestrogen has the capacity to suppress T cell-dependent DTH. To explore the mechanisms whereby oestrogen exerts its effects on the immune system we have used SCID mice which are largely devoid of functional T and B lymphocytes, hence being unable to raise DTH, but display intact antigen-presenting capacity. Transfer of lymphocytes to SCID mice restores the DTH capacity. In order to analyse if oestrogen down-regulates DTH by a direct action on T cells we reconstituted SCID mice with either splenocytes or thymocytes from congenic C.B-17 or allogeneic B6 donor mice. Either donor or recipient mice were exposed to estradiol before cell transfer. DTH response was registered in recipient SCID mice 1 and 3 weeks after challenge with oxazolone (OXA). SCID mice receiving estradiol-exposed spleen cells from congenic or allogeneic donor mice displayed lower DTH responses compared with control mice. In contrast, SCID mice receiving estradiol-exposed thymocytes from congenic donor mice showed no significant difference in DTH response compared with control mice. Estradiol-treated SCID mice, transferred with either spleen cells or thymocytes from congenic, hormonally non-treated donors, displayed a significantly lower DTH response compared with control mice. In contrast, estradiol-treated SCID mice receiving hormonally non-treated allogeneic spleen cells showed no difference in DTH response compared with control mice. The results show that T lymphocytes are not the target cell population for estradiol-mediated suppression of DTH in reconstituted female SCID mice.

Many immune-mediated inflammatory diseases are treated with corticosteroids. This type of treatment is, however, often afflicted with side-effects such as osteoporosis and atherosclerosis. During the last decades also sex steroids, such as estrogens, have been shown to have immunoregulatory properties. In this report we studied the effect of combined treatment with suboptimal doses of dexamethasone and estradiol on T lymphocyte mediated delayed type hypersensitivity (DTH), granulocyte-mediated inflammatory responses, immunoglobulin production and antigen specific antibody responses in mice. The results show that the two hormones display additive effects on suppression of DTH. In contrast, such additive effects were not observed in granulocyte-mediated inflammation. B lymphocyte activity, measured by immunoglobulin production and antigen-specific antibody responses, were increased after exposure to estradiol and suppressed by dexamethasone. In mice treated with both hormones the up regulation of B lymphocytes was still evident. The results could indicate the potential to use combinations of corticosteroids and estrogen in the treatment of T lymphocyte dependent rheumatic diseases such as rheumatoid arthritis (RA). In addition, the B lymphocyte stimulation by estrogen in cortisone exposed mice stimulate to future studies in humans if estrogen containing contraceptives or post menopausal hormone treatment could have triggering effects in patients with immune complex mediated diseases also when they are on corticosteroid treatment.

No abstract