Maria Elena Ferro

Delayed hypersensitivity and lesions following isoimmunization with modified rat male accessory glands: kinetics of induction

The kinetics of the cellular immune response to rat male accessory glands were studied in Wistar rats isoimmunized with modified rat male accessory glands extract and complete Freunds adjuvant at 0, 30 and 45 days. The animals were divided into seven groups, and each group was sacrificed weekly. One immunization was sufficient for the induction of 2-, 6- and 24-h footpad reactivity. The reaction increased until 21 days post-immunization. After the second injection the reaction decreased and was negative 12 days later. Migration inhibitory factor (MIF) activity monitored by a mixed-direct assay was demonstrated in rats from all groups except in the animals studied at day 42 in which macrophage migration was markedly stimulated. The absence of MIF activity correlated with a lack of delayed type hypersensitivity (DTH) response. The humoral response was studied and detected by passive hemagglutination in a few sera after the first immunization. A second injection was necessary to obtain a more frequent occurrence and higher titres of antibodies. Histological modifications in the target organs started to appear in the group of animals studied at 35 days and were characterized by a mononuclear infiltrate in the prostate, coagulating glands and seminal vesicles. In several cases there was also infiltration of polymorphonuclear cells. Specimens obtained at 35 days showed the most severe lesions.

Non-specific immunosuppression in experimental cryptococcosis in rats

The delayed type hypersensitivity response to human serum albumin (HSA) of rats infected intraperitoneally with 107 viable C. neoformans cells, and 7 days after, immunized with human serum albumin was significantly diminished (p<0.05) when compared with the response observed in rats immunized with human serum albumin and non infected. The spleen mononuclear cells from suppressed rats transferred to normal syngeneic recipients of the same sex suppress the afferent phase of the response (p<0.02) suggesting that cells present in the spleen might be one of the responsible mechanisms for the suppression to nonrelated antigens in infected animals.

Enhanced myocardial lesions in chronically Trypanosoma cruzi-infected rats subjected to adult thymectomy

Control animals and rats infected 90 days earlier, by inoculation of 1 x 10(6) trypomastigotes of Trypanosoma cruzi at weaning, were subjected to adult thymectomy (ATx) or sham operation (S-ATx) and assessed 3 months later for the presence of myocardial lesions and levels of lymph node and spleen T-cell populations. Chronic focal myocarditis (CFM) developed in 78% and 84% of S-ATx or ATx infected rats, respectively. While the two groups of infected rats did not differ as to the occurrence of myocardial lesions, large foci of CFM were more prevalent in ATx infected rats. Chronic T. cruzi (Tc) infection resulted in decreased CD4+ and increased CD8+ lymph node and spleen cell, with CD8+ lymphocytes being lowered to normal values in the spleen of the ATx infected group. It is suggested that ATx might act by interfering with a down-regulating immunoregulatory mechanism, leading to an exacerbation of autoimmune reactions believed to be involved in the generation of myocardial damage.

Adoptive transfer of suppression of the autoimmune response to rat male accessory glands: characterization of the suppressor cells

We have examined the mechanism of suppression of autoimmunity to rat male accessory glands (RAG) by T suppressor cells. This suppression was accomplished by transfer to syngeneic rats of spleen mononuclear (SpM) cells from rats rendered unresponsive by pretreatment with low doses of a purified fraction of RAG (containing the autoantigen). The experiments demonstrated that the suppressor cells that act on the inducer phase of the suppression are cyclophosphamide (Cy) sensitive and that they can be positively selected on antigen-coated plates. On the other hand, the inducer phase T suppressor cells present on spleens coming from antigen-pretreated rats did not suppress the autoimmune response in normal recipients that had been irradiated (850 rad 137Cs) just prior to receiving the cells or injected with Cy 14 days after transfer. The results indicate that the regulation of immune response to the autoantigen of RAG is complex and that it involves the interaction of many cell types.

Antigen-induced inhibition of autoimmune response to rat male accessory glands: distinct characteristics of I-A- and I-E-positive peritoneal cells.

The present report describes different aspects of two populations of peritoneal cells (PC) obtained from rats injected i.p. 2 h or 24 h previously with a suppressor dose of a purified fraction (FI) of rat male accessory glands (RAG) (FI‐PC2h and FI‐PC24h, respectively). The FI‐PC2h, which are mainly I‐E (OX17) positive and can suppress the autoimmune response to RAG autoantigens, have an elevated phagocytic activity against Candida albicans and capacity to reduce the dye nitroblue tetrazolium. In contrast, FI‐PC24h, which are mainly I‐A (OX6) positive and can potentiate the autoimmunity to RAG autoantigens, have a diminished capacity to reduce the dye and a diminished phagocytic activity. Moreover, the Toxoplasma gondii appear to have a different effect on both populations. The parasites can invade FI‐PC2h while FI‐PC24h offer resistance to T. gondii aggression.

Effect of aging on autoimmune response to rat male accessory glands: young, but not aged, antigen-presenting cells efficiently induce suppression in aged rats

The present report analyzes the suppressor cell system of aged rats in an experimental model of autoimmunity to rat male accessory glands (RAG). A state of specific suppression to RAG was induced when young rats are pretreated with peritoneal cells (PC) obtained from syngeneic young rats i.p. injected 2 h previously with chromatographic fraction I (Sephadex G-100) (FI) of RAG (yFI-PC). Although the yFI-PC injection diminished the DTH in aged rats the autoimmune response remained positive. Peritoneal cells obtained from aged rats injected with FI of RAG (oFI-PC) did not suppress the DTH response in either aged or young rats. In both young and aged, pretreatment with yFI-PC stimulates spleen cells capable of inducing suppression (inductor-phase suppressor cells) when they are transferred to young recipients. However, the spleen inductor-phase suppressor cells of 12-month-old rats are unable to suppress the autoimmune response in their own aged environment. To obtain effective suppression in 12-month-old rats, the injection of yFI-PC was necessary prior to and subsequent to immunization. In this work we observe that 12-month-old rats could efficiently induce inducer phase and effector-phase suppressor cells when the adequate young antigen-presenting cells were present to stimulate them.

Specific neonatally-induced tolerance to rat male accessory glands antigens. Transference of specific suppression by spleen mononuclear cells

The immune response of infant rats was studied following (1) immunization of their mothers with modified rat male accessory glands (MRAG) emulsified in complete Freunds adjuvant (CFA), (5 mg/ml or 25 mg/ml) or with human serum albumin (HSA), (5 mg/ml or 25 mg/ml) and (2) intradermal immunization of the offspring at 21 days of age with 5 mg of MRAG-CFA and 5 mg of HSA-CFA. Antibodies to MRAG or to HSA were observed in the sera obtained 20 days after the birth of the offspring. Delayed hypersensitivity (DTH) against MRAG studied 13 days after immunization was significantly reduced in the male offspring born to mothers immunized with 5 mg of MRAG-CFA compared with that of males born to mothers immunized with the same dose of HSA-CFA (P less than 0.0005). In contrast, when 25 mg of MRAG-CFA were used to immunize the mothers, the lack of DTH response to MRAG was observed in male and female offspring (P less than 0.0005 for both groups). In all cases, the DTH response to HSA was positive. The spleen mononuclear (SpM) cells transferred from rats unresponsive to MRAG to normal rats 24 h before the immunization with MRAG-CFA and HSA-CFA did not suppress the immune response whereas transference of SpM cells from suppressed animals to animals previously immunized depressed the DTH response to MRAG (suppression of the expression). The response to HSA was not affected. We can conclude that the suppression is antigen specific.

Antigen-induced inhibition of autoimmune response to rat male accessory glands. Role of macrophages in the induction of suppressor cells

The present paper describes a mechanism responsible for the induction of inducer-phase suppressor cells effective to suppress the autoimmune response to rat male accessory glands (RAG). In fact, we reported here that marked suppression of delayed type hypersensitivity (DTH) reaction and humoral response to chemically modified rat male accessory glands (MRAG) can be obtained when previously to be immunized with MRAG in complete Freunds adjuvant (CFA) syngeneic rats were pretreated with peritoneal cells (PC) coupled with a purified fraction of RAG (containing the autoantigen). The involvement of MRAG-specific inducer-phase suppressor cells was demonstrated by adoptive transfer experiments of spleen mononuclear cells from unresponsive donors to normal syngeneic rats 24 h prior to immunization of the recipients with MRAG-CFA. The PC used to treat the animals show a large proportion of non-specific-esterase positive, Ox-41 bearing macrophage-like cells. Moreover, the antigen-coupled PC able to trigger the suppressor cells showed the presence of the autoantigen of RAG on their surface. The role of the antigen presenting cells in the induction of MRAG-specific inducer-phase suppressor cells is discussed.

Antigen Induced Inhibition of Autoimmune Response to Rat Male Accessory glands: Role of Thymocytes on the Efferent Phase of the Suppression

In the present study, we report that Cy-sensitive, MRAG-adherent spleen mononuclear (SpM) inductor-phase T suppressor (Ts) cells obtained from rats pretreated with low doses of a purified fraction (FI) of rat male accessory gland antigens (RAG) are mainly OX19+ and W3/25+. Furthermore, thymocytes from rats pretreated with FI of RAG restore the suppression of the autoimmune response to RAG autoantigens in irradiated recipients of SpM inductor-phase Ts cells. In contrast, thymocytes from rats pretreated with rat heart saline extract (unrelated antigen) did not recuperate the suppression of the autoimmune response detected by macrophage migration inhibitory factor (MIF) and delayed-type hypersensitivity. The suppressor thymocytes did not directly exert their inhibitory effect because they were not effective to suppress the autoimmune response to RAG autoantigens when irradiated recipients did not receive SpM inductor-phase Ts cells. The effect of these thymocytes was found in PNA--but not in PNA+ thymic cell population. The perithymic injection of Toxoplasma gondii did block their suppressor activity. The present report clearly shows an active participation of thymus in the efferent phase of the suppressor circuit that controls the autoimmune response to MRAG. The implications of these findings are discussed.

Effect of Gangliosides in the Autoimmune Response Induced by Liposome-Associated Antigens

A model of autoimmunity to rat male accessory glands (RAG) was recently developed by intraperitoneal administration of three doses of native RAG associated with liposomes. In this work we analysed the effects of gangliosides in the cellular response to RAG when they were intraperitoneally administrated prior to the second dose of liposome-associated RAG. Results show that the ganglioside treatment could modify an established DTH response. Also, gangliosides markedly reduced the number of Ia antigen-positive peritoneal exudated cells (PEC). However, they modified neither the processing of liposomes through PEC nor their viability. Moreover, we obtained cellular response by transferring PEC from immunized donors into naive receptors.