Rat Male Accessory Glands Research Articles

Expression of transforming growth factor-beta isoforms in the rat male accessory sex organs and epididymis.

We studied the expression and distribution of transforming growth factor-beta (TGF-beta) isoforms in the rat male accessory sex glands and the epididymis. Our data demonstrate the expression of both TGF-beta1 and -beta3 isoforms in ventral prostate (VP), seminal vesicle (SV), coagulating gland (CG), and epididymis (E) by Northern blot analysis. In addition, there was differential expression of TGF-beta3 in the three regions of epididymis, the corpus region being the highest. Immunostaining data showed intense staining for latent TGF-beta1 in all the male accessory glands. In contrast, no staining using antibodies specific for active TGF-beta1 was observed. No expression of TGF-beta2 was evident either by immunohistochemistry or Northern blot analysis. The presence of mature TGF-beta3 protein was observed in the secretory epithelium of VP, CG, and corpus E. There was no detectable staining of TGF-beta3 in the seminal vesicle and caput and cauda regions of epididymis. These data suggest possible differential regulation of TGF-beta isoform expression in the male reproductive system and predict unique roles for individual TGF-beta isoforms in sperm maturation and maintenance.

Involvement of Peritoneal Dendritic Cells in the Induction of Autoimmune Prostatitis

We have been working within a model of autoimmune prostatitis induced by the intraperitoneal administration of saline extract of rat male accessory glands (RAG) associated to liposomes. The intraperitoneal administration of RAG-liposomes elicits both primary and secondary cellular autoimmune responses to RAG as well as organ-specific lesions. To evaluate the participation of dendritic cells (DC) in the induction of the autoimmune response, we purified peritoneal DC (PDC) after a single injection of RAG-liposomes and we characterized this population by morphology and phenotype. Based on adherence and morphologic criteria, we determined that PDC comprised approximately 1% of the total peritoneal cells. The ultrastructure of the dendritic cell enriched fraction was assessed by electron microscopy. By FACS analysis, PDC showed a two to three-fold increase in expression of the IA molecule compared to macrophages. They expressed low but positive levels of the CD14 marker, and intermediate levels of both CD11b (Mac-1) and CD54 (ICAM-1) adhesion molecules. In addition, PDC transferred either intra-venously or intraperitoneally efficiently elicited the autoimmune response to RAG in normal receptors. These results support the involvement of peritoneal dendritic cells in the induction of autoimmune prostatitis, modifying the idea of macrophages as the single antigen presenting cell in the peritoneal cavity.

Mast Cells in Accessory Glands of Experimentally Induced Prostatitis in Male Wistar Rats

We studied the histological modificatious in the accessory glands of autoimmune rats. Adult male Wistar rats were id immunized three times with saline extract of rat male accessory glands (RAG) chemically modified (MRAG) in complete Freund's adjuvaut (CFA) (groups 1, 2, and 3). Prior to the first immunization with MRAG-CFA groups 2 and 3 received peritoneal cells obtained from rats that had been injected 2 or 24 hr previously with low doses of RAG. Furthermore, an additional group (group 4) ip immunized with liposome-associated-RAG was incorporated. The delayed-type hypersensitivity response studied 10 or 15 days after first immunization was positive for rats of groups 1, 3, and 4, while it was negative for rats of group 2. Serum samples obtained on Day 45 and studied by ELISA showed high levels of autoantibodies in groups 1 and 2 and lower levels of autoantibodies in group 3, but did not show autoantibodies in group 4. The histological studies performed 10 days after the last immunization showed organ-specific lesions in the accessory glands in animals of groups 1, 3, and 4. Infiltration of mononuclear cells was the main alteration in group 1, while infiltration of mast cells and polymorphonuclear leukocytes were present in specimens of groups 3 and 4. The main finding of this study was a significant increase ( P < 0.0005) in the extent of mast cell degranulation in the specimens of accessory glands stained with toluidine blue. Our results suggest that mast cells are activated in our experimental model of autoimmune disease.

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.

Effects of thymus supernatants on the phenotype of different subsets of peritoneum antigen-presenting cells.

Peritoneal cells (PC) obtained 2 h subsequent to intraperitoneal (i.p.) injection of low doses (200 micrograms) of a purified fraction of rat male accessory glands (FI-RAG) are phenotypically and functionally different from those obtained 24 h after i.p. injection. In fast, PC obtained 2 h after FI-RAG injection are mainly IE+ and are involved in inducing specific suppression to RAG. In contrast, PC obtained 24 h after FI-RAG injection are mainly IA+ and capable of inducing specific response to RAG. For their induction, IA+ PC require cells within or recently derived from bone marrow. In order to analyze the mechanisms involved in IA+ bone marrow-dependent cell generation in the peritoneum, we studied the distribution of FI-RAG following i.p. injection. It was established that FI-RAG is found mainly in the thymus 2 h after injection and remains there for at least 24 h. Subsequently, we analyzed, in 4 groups of rats, the influence of thymic culture supernatants on the phenotype of cells appearing in the peritoneal cavity 2 h after FI-RAG injection. An increase in IA+ PC was observed 2 h after i.p. injection of FI-RAG in animals that had received either supernatants from normal thymic cells cultured with FI-RAG or those from thymic cells taken from animals injected with FI-RAG 2 h prior to being killed. Supernatants of thymic cells from animals injected with FI-RAG 24 h prior to being killed or from normal thymic cells do not increase the percentage of IA+ PC.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of an immunoregulatory cell subset involved in the up-regulation of the autoimmune response to rat male accessory glands.

We studied the regulation of the autoimmune response to rat male accessory glands (RAG) using liposomes as adjuvants. Adult male Wistar rats were submitted to three intraperitoneal (i.p.) immunizations with 750 micrograms of saline extract of RAG associated with liposomes. The delayed type hypersensitivity (DTH) response studied approximately 10 days after each immunization developed after the first immunization, having a remission state after the second one and a clear increase after the third injection. In a further study, spleen mononuclear (SpM) cells obtained form immunized rats 10 days after the third immunization (DTH positive) or from normal rats were separated as adherent (VV+) or nonadherent (VV-) to Vicia villosa population. In VV+ SpM cells from immunized or normal animals an enhanced percentage of OX8+ cells (P < .05 and P < .01, respectively) was found, but in VV- SpM cells from the same groups of rats an enhanced percentage of W3/25+ cells (P < .01 and P < .05, respectively) was found when they were studied by immunofluorescence. Later on, we transferred total VV+ or VV- SpM cells from i.p. immunized rats to immunized recipients 10 days after the second immunization (DTH negative). The DTH response was enhanced in recipients of total or VV+ SpM cells (P < .01). It was also observed that the transfer of VV- SpM cells from immunized rats or total or VV+ SpM cells from normal rats did not reduce the suppression state observed after the second injection (P = NS). The total SpM cells obtained 10 days after the third immunization (DTH positive) were able to transfer autoimmune response to RAG to normal animals (P < .01), whereas VV+ SpM cells did not show that capacity (P = NS).

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.

Antigen-induced inhibition of the autoimmune response to rat male accessory glands: bone marrow dependence of the enhancement of IA+ but not IE+ antigen-presenting cells.

IE+ peritoneal cells (PC), involved in the induction of suppression of autoimmune response to rat male accessory glands (RAG), are obtained from rats 2 h after i.p. injection of a purified fraction (FI) of RAG (FI-PC2h). In contrast, IA+ PC, involved in the induction of autoimmune response to RAG, are obtained from rats 24 h after FI of RAG injection (FI-PC24h). The present report analyzes the effect of irradiation or irradiation/bone marrow reconstitution on the induction of both populations of PC. Peritoneal cell donor rats were irradiated in a telegamma therapeutic Cs137. Twenty hours later half of them were i.v. reconstituted with 40 x 10(7) bone marrow cells. Six days later rats were i.p. injected with 200 micrograms of FI of RAG and 10(7) resident PC. The PC were harvested 2 h or 24 h later. The ability of resident PC to yield IE+ FI-PC2h involved in the induction of suppression is not impaired by irradiation, but the ability of resident PC to yield IA+ FI-PC24h involved in the induction of a positive response is impaired by irradiation and restored by bone marrow reconstitution of irradiated rats. Culture of normal PC with FI of RAG for 2 h or 24 h shows a selective increase in IE+ cells able to induce suppression to RAG.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of aging on the autoimmune response to rat male accessory glands: deficit of I‐E‐positive peritoneal cells capable of inducing suppression

The present report analyzes the ability to induce suppression to rat male accessory gland (RAG) autoantigens and the characteristics of T suppressor (Ts)-inducer peritoneal cells (PC) in old rats which show increased autoimmune responses. The injection of young rats with a purified fraction (FI) of RAG 10 and 3 days prior to immunization with chemically modified RAG (MRAG) markedly reduced the immune response to RAG autoantigens when compared with young rats which had only been immunized (controls), while the pretreatment of old rats did not block the delayed-type hypersensitivity reaction to MRAG when compared with control old rats. The study of cell surface markers on PC from rats injected i.p. 2 h previously with FI of RAG (FI-PC) showed an increase of OX-6 (I-A) and a decrease of OX-17 (I-E) in FI-PC of old rats with respect to FI-PC of young animals, which showed a selective increase of I-E+ Ts-inducer PC. The i.p. injection of FI-PC from old rats into young recipients, 10 and 3 days prior to immunization with MRAG in complete Freund's adjuvant, did not modify the autoimmune response when compared with controls. By contrast, the injection of young and old rats with FI-PC from young animals induced a significant suppression of the autoimmune response. The reduced percentage of I-E+ suppressor-inducer PC provides an explanation for the diminished ability to induce suppression to RAG autoantigens in old rats.

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. FI-PC2h cultured during 22 h (FI-PC2-24h in vitro), or PC obtained from syngeneic recipients injected i.p. 22 h previously with FI-PC2h (FI-PC2-24h in vivo) show, as FI-PC2h, an increase of the I-E+ cells and capacity to induce suppression of the delayed-type hypersensitivity response to RAG autoantigens when they are injected to syngeneic rats 10 and 3 days prior to the immunization with chemically modified (diazotized arsanilic and sulfanilic acid) RAG in complete Freund's adjuvant. The PC obtained 24 h after injection of irradiated rats with N-PC plus FI show an increase of I-E+ cells whereas an enhancement of I-A+ cells can be observed when the PC are obtained 24 h after injection of irradiated and bone marrow-reconstituted rats with N-PC plus FI. These findings appear to indicate that FI-PC2h and FI-PC24h are functionally different and that the population obtained 24 h after injection of FI of RAG could not originate from either the population present 2 h after injection of FI of RAG injection nor from normal PC. They appear to require bone marrow precursors.

Adjuvant effect of liposomes in the autoimmune response to rat male accessory glands

Wistar rats submitted to 3 intravenous (i.v.) or intraperitoneal (i.p.) immunizations with saline extract of rat male accessory glands (RAG) associated to liposomes developed a delayed type hypersensitivity (DTH) response to RAG after the first immunization, a remission state after the second immunization and a specific DTH response after the third injection. In a further study we transferred spleen mononuclear (SpM) cells from i.p. immunized rats taken 10 days after the second immunization (DTH negative) to normal or immunized recipients 24 h before or 10 days after the first immunization with RAG liposomes, respectively. The DTH response was reduced only in recipients previously immunized. Besides, it was possible to show that the transfer of SpM cells present when the response increased after the third injection in i.p. immunized donors reduced the suppression observed after the second injection. Rat accessory gland biopsies taken 10 days after the last immunization showed in nearly all cases mast cells, plasma cells and eosinophils with scarce lymphoid elements and increased acinar desquamation. This kind of infiltration had characteristics of cutaneous basophil hypersensitivity.

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.

Maternal‐Fetal Interactions on the Regulation of the Autoimmune Response

Adult female rats were immunized with 5 mg or 25 mg of modified rat male accessory glands (MRAG) incorporated to complete Freund's adjuvant (CFA) before, during, and after pregnancy. The mothers and litters were exchanged between the experimental and normal groups. The offspring were brought up to 20 days of age and immunized with 5 mg of MRAG-CFA and 5 mg of human serum albumin (HSA)-CFA. Anti-MRAG antibodies were detected in the offspring brought up by the immunized mothers and the titers were similar to those of the foster mothers whereas in the offspring of the experimental group fostered by normal mothers antibodies to MRAG were not detected. The DTH performed in the offspring 13 days after the immunization was significantly diminished in male and female offspring from the 5 mg and 25 mg experimental group fostered by normal mothers (P less than 0.0005 for all groups). Similar results were found when the offspring from normal mothers were suckled by mothers immunized with MRAG-CFA. To assess whether MRAG or HSA administered to female rats reached the offspring via the placenta or the milk, female rats were immunized with 3 mg of 125I-MRAG-CFA or with 3 mg of 125I-HSA-CFA. When radioactivity was measured in neonates (n = 11) that were suckled by the 125I-MRAG-CFA immunized mothers, the specific activity was 116 in stomach (0.4 micrograms of MRAG) and 940 in the total organs (3.8 micrograms of MRAG).(ABSTRACT TRUNCATED AT 250 WORDS)

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

The present report describes the structural and functional characteristics of the population of peritoneal cells (PC) from rats injected intraperitoneally (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). Both populations of PC showed the presence of the autoantigens of RAG on their membrane. The study of cell surface marker showed increase of OX17 (I-E) in FI-PC2h and OX6 (I-A) in FI-PC24h. I.p. injection of FI-PC2h 10 and 3 days prior to immunization with chemically modified (diazotized arsanilic and sulfanilic acid) RAG (MRAG) in complete Freund's adjuvant induced suppression of the delayed-type hypersensitivity (DTH) response to MRAG, whereas the i.p. injection of FI-PC24h induced potentiation of DTH response to MRAG when compared with controls (animals injected 10 and 3 days prior to immunization with PC from rats injected i.p. with an unrelated antigen). The treatment of FI-PC2h with OX17 and FI-PC24h with OX6 prior to the transfer blocked the suppression and potentiation described above. These findings show that the i.p. injection of an FI of RAG at a suppressor dose induces PC with immunologically opposite characteristics, depending on the time of obtention.

Potentiation of Autoimmune Response in Rats Infected with Toxoplasma Gondii . Inhibition of Suppressor System and Impairment of Thymic Cellular Populations

In the present work we studied the influence that an infection with Toxoplasma gondii in thymus proximity produces on the suppression of autoimmune response to autoantigen of rat male accessory glands (RAG). The suppression was achieved injecting syngeneic animals with low doses of autoantigen of RAG previous to the immunization with chemically modified rat male accessory glands (MRAG). Rats were infected in thymus proximity with 3 x 10(3) trophozoites of T. gondii before or after to be suppressed. Controls were rats only infected or only suppressed. The delayed hypersensitivity response against MRAG, (DTH test), was significantly potentiated in rats only infected and in the animals suppressed before the infection (p less than 0.001). The suppression was not inhibited in the animals suppressed after infection. The suppression of humoral response against MRAG studied by ELISA and passive hemagglutination test was prevented in rats infected before as well as in rats infected after the induction of suppression (p less than 0.001). Decrease of CD4+ CD8+ and Ox18+ (class I MHC antigen) and increase of CD4+ CD8- and CD4- CD8- thymocytes was observed in the rats where the DTH response was potentiated. These results indicate that the infection with T. gondii in thymus proximity was able to inhibit the suppression of response to autoantigen of RAG producing selective impairment in thymic suppressor influence.

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 Freund's 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 < 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 < 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 Freund's 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.

Participation of different cellular types in the enhancement of autoimmune response of old animals to sex accessory glands in male rats: importance of macrophages

In a previous work, we showed that the immunization of male rats, 3 and 12 months old, with saline extract of rat male accessory glands chemically modified (MRAG) and human serum albumin (HSA) induced a higher humoral and cellular autoimmune response in old animals than in young ones. We have also demonstrated that the facilitation of the autoimmune response is transferred by spleen total cells of 12-month-old animals. The immune response to HSA was not modified. In this work, the cellular type involved in such facilitation was analyzed. For this transference experiment, cells enriched in T and B lymphocytes and macrophages were used. The results showed that the macrophage is the main cellular type involved. However, the transference was only total with the three cellular types together. The study, performed with macophages pulsed in vivo with MRAG-HSA and then transferred to normal recipients, indicated that although the macrophages from young and old animals were capable of presenting the antigens, the latter did this with significantly greater efficiency for the autoantigen.

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 Freund's 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.

Effect of aging on the autoimmune response to sex accessory glands in male rats

The effect of aging on the immune response to autoantigen of rat male accessory glands (RAG) was studied in Wistar rats. Male and female rats, 3 and 12 months old, were immunized with chemically modified RAG and heterologous antigen (human serum albumin, HSA). The study of delayed type hypersensitivity (DTH) and antibodies against RAG revealed a higher response in 12-month-old animals than in 3-month-old animals ( P < 0.005), regardless of their sexes. No differences in DTH and humoral responses to HSA were observed. Experiments on the transfer of spleen cells showed an increase in response elicited by RAG immunization in young recipients of cells from normal or immunized old syngeneic donors. On the contrary, old recipients of spleen cells from normal or immunized young donors maintained their high response the same as non-transferred old rats. Therefore, both the lymphoid cells and the environment in which the response was elicited seem to be involved in the increase of the autoimmune response.