Orchidectomy and the immune response. I. Effect of orchidectomy on lymphoid tissues of mice

Luteinizing hormone-releasing hormone enhances T cell recovery following allogeneic bone marrow transplantation

Posttransplant immunodeficiency, specifically a lack of T cell reconstitution, is a major complication of allogeneic bone marrow transplantation. This immunosuppression results in an increase in morbidity and mortality from infections and very likely contributes to relapse. In this study, we demonstrate that sex steroid ablation using leuprolide acetate, a luteinizing hormone-releasing hormone agonist (LHRHa), increases the number of lymphoid and myeloid progenitor cells in the bone marrow and developing thymocytes in the thymus. Although few differences are observed in the peripheral myeloid compartments, the enhanced thymic reconstitution following LHRHa treatment and allogeneic bone marrow transplantation leads to enhanced peripheral T cell recovery, predominantly in the naive T cell compartment. This results in an increase in T cell function in vivo and in vitro. Graft-versus-host-disease is not exacerbated by LHRHa treatment and graft-versus-tumor activity is maintained. Because LHRHa allows for reversible (and temporary) sex steroid ablation, has a strong safety profile, and has been clinically approved for diseases such as prostate and breast cancer, this drug treatment represents a novel therapeutic approach to reversal of thymic atrophy and enhancement of immunity following immunosuppression.

Augmentation of T cell levels and responses induced by androgen deprivation

Androgen has been implicated as a negative regulator of host immune function and a factor contributing to the gender dimorphism of autoimmunity. Conversely, androgen deprivation has been suggested to potentiate male host immunity. Studies have shown that removal of androgen in postpubertal male mice produces an increase in size and cellularity of primary and peripheral lymphoid organs, and enhances a variety of immune responses. Yet, few details are known about the effect of androgen removal on T cell-mediated immunity. In this study, we demonstrate two pronounced and independent alterations in T cell immunity that occur in response to androgen deprivation, provided by castration, in postpubertal male mice. First, we show that levels of T cells in peripheral lymphoid tissues of mice are increased by androgen deprivation. Second, T cells from these mice transiently proliferate more vigorously to TCR- and CD28-mediated costimulation as well as to Ag-specific activation. In addition, androgen deprivation accelerates normalization of host T and B cell levels following chemotherapy-induced lymphocyte depletion. Such alterations induced by androgen deprivation may have implications for enhancing immune responses to immunotherapy and for accelerating the recovery of the immune system following chemotherapy.

Reversal of ageing changes in the thymus of rats by chemical or surgical castration

Differences in the thymus of young and old male CSE Wistar rats were examined by use of routine histological stains on paraffin-embedded sections. There was a highly significant loss of thymic weight and disruption of architecture with age. Both surgical castration and chemical castration induced by a luteinizing hormone-releasing hormone analogue (Goserelin) caused a significant increase in thymic weight and the reappearance of a well-defined cortex and medulla in ageing rats. Cell surface antigens were detected on cryosections after incubation with a range of monoclonal antibodies. The Pan T cell marker (detected with antibody W3/13) showed fewer positive cells in ageing rats, and an increase after chemical castration. The smaller glands of old rats had fewer positive T cells with CD4 (MRC OX35) and CD8 (MRC OX8) antigens, and more after chemical castration in both young and ageing rats, but the greatest changes were seen in the intensity of Class II major histocompatibility complex (MRC OX6) immunoreactivity. In both young and ageing chemically-castrated rats, the number of cells and the intensity of immunoreactivity were greatly increased in the medulla.

Effect of a rice-rich diet on the therapeutic efficacy of cyclophosphamide with special reference to the enhancement of transplantation immunity

The present study investigated the problem of whether the therapeutic efficacy of cyclophosphamide in the in vivo Ehrlich ascites tumor system can be improved by adjuvant use of hydrocortisone or of dietary hydrocortisone mobilizers. In the chemotherapy experiment, female ICR mice each received an inoculum of 1 x 10(6) cells of Ehrlich ascites tumor ip followed by 2 ip injections of cyclophosphamide 36 and 37 hr later (2.4 mg/mouse for the 1st injection, and 1.0 mg/mouse for the 2nd injection). The effects of both cyclophosphamide and adjuvant treatments were assessed in terms of either survival rate or cure rate in the 1-month experiment. The results obtained were as follows. 1) Prolonged use of hydrocortisone as an adjuvant can improve the survival of cyclophosphamide-treated mice. 2) Adjuvant use of a rice-rich diet for maintenance increased the rates of both survival and cure in the cyclophosphamide-treated mice. 3) The same maintenance of mice on a rice-rich diet increased transplantation immunity on the one hand, and induced a set of steroidal changes including hydrocortisone excess on the other hand. 4) Evidence is presented to indicate that the beneficial influence of a rice-rich diet on the drug effect is related to an increase of transplantation immunity in the host, and that there could be a causal relationship between hormonal and immunological changes in rice-saturated mice.

An influence of diet on transplantation immunity

It was discovered by chance that mice raised under otherwise entirely conventional conditions of husbandry but fed upon autoclaved diet (diet A) had stronger cell-mediated immune reactions than those of mice raised under the same conditions but with an unmodified diet (diet B) : skin allografts were rejected more quickly, transplantation tolerance was more difficult to procure and fibrosarcomas induced by the injection of methylcholanthrene (MCA) arose more slowly and less often. Analysis showed that these findings could be explained at least in part by the discovery of Mertin & Hunt (1976, p. 928) that a partial deprivation of polyinsaturated fatty acids led to an intensification of cell-mediated immunity; on the other hand, experiments with dietary mixtures made it seem unlikely that this was the whole explanation and pointed towards some positive immunopotentiation by an ingredient of autoclaved diet. This, it was proposed, might be a compound of unknown composition resulting from the interaction of vitamin A with other dietary constituents. This interpretation was not supported by direct evidence but by confirming that retinol derivatives, especially retinyl acetate, could exercise an immunopotentiation of the kind and degree under investigation: retinyl acetate could counteract the immunosuppressive action of linoleic acid, though retinyl methyl ether was ineffective. Although retinyl derivatives may protect against MCA tumours by impeding its metabolic conversion to an oncogenic form, the effects of an autoclaved diet upon skin allograft survival, the induction of tolerance and the formation of tumours is probably mediated through an immunological mechanism.

Orchidectomy and the immune response. III. The effect of orchidectomy on tumour induction and transplantation in mice

The effects of orchidectomy in Balb C mice on the induction and transplantation of tumours which are not obviously hormone dependent were studied. Orchidectomy prolongs the interval between subcutaneous injection of methylcholanthrene and appearance of subcutaneous sarcoma. In tumour transplantation experiments orchidectomy conferred a slight but significant protective effect when meth A tumour cells (which are syngeneic with Balb C mice) were grown in ascitic form and when the same cells grew as a solid subcutaneous tumour protection was increased. Protection was counteracted by administration of a.l.s. and partially abrogated by thymectomy combined with orchidectomy, findings that suggest alteration of cell mediated immunity as the mechanism of protection. Combination of cyclophosphamide treatment with orchidectomy increased the antitumour effect of orchidectomy alone. In contrast orchidectomy accelerates the appearance of spontaneous leukaemia in AKR mice which is known to be thymus dependent. The explanation is probably that orchidectomy, by causing thymic hypertrophy increases the number of cells at risk of malignant transformation. It is suggested that some of the beneficial effects of the endocrine treatments of cancer may result from alteration of host immunity and have therefore, a range of application wider than in the management of endocrine dependent tumours alone.

Orchidectomy and the immune response. II. Response of orchidectomized mice to antigens

The responses of orchidectomized mice to several antigens have been investigated. Orchid-ectomy was associated with an accelerated rejection of skin allograft, which was prevented by androgen administration, abrogated by anti-lymphocyte serum and potentiated by cyclophosphamide. Reactivity of orchidectomized mice to oxazolone, sheep red blood cells and graft versus host disease, which are limited by thymus-processed cells, was increased whereas production of antibodies to bovine serum albumen, skin allografts and pneumococcal poly-saccharide was unchanged. It is proposed that orchidectomy augments cell mediated immune responses, but has no direct effect on responses transacted mainly by B cells. The effect of cyclophosphamide may be due to the withdrawal of a restraining influence on cell mediated immunity normally exercised by humoral antibody.