Modulation of Leydig cell testosterone production by secretory products of macrophages.

Unstimulated macrophages from testes inhibited the production of testosterone by Leydig cells from adult, but not immature, Sprague-Dawley rats (significant after 48 h). Similar results were observed with unstimulated macrophage-conditioned media, suggesting that the observed effect was mediated by one or more secretory products. None of these substances was interleukin-1, since macrophage supernatants tested negative in an interleukin-1 alpha and interleukin-1 beta sensitive, thymocyte assay. Interleukin-6 was detected by a B cell proliferation assay. After stimulation by LPS, testicular macrophages enhanced testosterone production by Leydig cells from adult and immature rats. This enhancement was dose-dependent and required low concentrations (but over 2.5%) of conditioned media. Interleukin-1 and interleukin-6 activities were detected in LPS-stimulated macrophage supernatants. Supernatants of LPS-stimulated, human monocytes had similar effects on Leydig cells. They were rich in interleukin-1, interleukin-1 receptor antagonist and interleukin-6. The present study suggests that, in adult rats, testicular macrophages modulate Leydig cell steroidogenesis by secretory products whose secretion depends on the physiological state of macrophages. The factor or factors responsible for stimulation are not species-specific. The effect cannot be accounted for by variations in the concentration of the above mentioned interleukins in macrophage supernatants.

IL-1 receptor antagonist in saliva; characterization in normal saliva and reduced concentration in Sjögren's syndrome (SS).

The characterization of a salivary factor cross-reacting with IL-1 receptor antagonist (IL-1Ra) is described. The apparent molecular weights of two species were 23 kD, consistent with the secreted peptide (sIL-1Ra), and 20 kD, consistent with the intracellular peptide (icIL-1Ra). It had an inhibitory activity on IL-1-stimulated fibroblasts, which is characteristic of IL-1Ra. Its source was the oral mucosa and not the salivary glands. Saliva from patients with SS contained significantly less IL-1Ra than saliva from controls. The decrease was marked in patients with early dental loss but whose xerostomia was still partial. In SS, the salivary IL-1/IL-1Ra imbalance may promote inflammatory lesions in the mouth and impede mucosal cell differentiation.

Discrepancy between 3H-thymidine uptake and cell cycle studies in stimulated lymphocyte cultures treated with methotrexate.

The mode of action of methotrexate (MTX) in rheumatoid arthritis (RA) is unknown. The hypothesis that its cytostatic effect may be involved has been questioned based on the evidence of several negative results, the most intriguing being its lack of effect on the Lymphoblastic Transformation Test (LTT) and other lymphoproliferations in cultures from patients' samples. Our study demonstrates that LTT evaluation by 3H-thymidine uptake, a standard method, is misleading when applied to MTX-treated cells. At in-vitro concentrations similar to those present in the red blood cells of RA patients, MTX produced an early block in the cell cycle without reducing the cellular uptake of 3H-thymidine. While the explanation of this discrepancy is still open to discussion, it is clear that future studies on the immunological status of RA patients on MTX should not use thymidine uptake for the measurement of the lymphocyte response to mitogens and various stimuli, but must rely on other methods for evaluating DNA synthesis.

Ultrastructural and immunohistochemical evidence of in situ differentiation of mononuclear phagocyte system cells in the interstitium of human fetal testis.

Ultrastructural and immunohistochemical studies were made of the testicular interstitial tissue from eight human fetuses of 15 to 27 weeks gestation. Three cell types developed in mesenchymal cells: Leydig cells and peritubular cells, as already reported, and cells of the mononuclear phagocyte system (MPS), which are located in the intermediate area of the interstitial tissue. Located at the periphery of Leydig cells, these gradually differentiate between 16 and 20 weeks and later acquire the ultrastructural characteristic of histiocytes during the involution phase of the fetal testis. Immunohistochemical studies using monoclonal antibodies (Mo Ab) to antigens of human myelomonocytic cells isolated a cell subpopulation in the interstitial tissue that is distinct from the peritubular (fibroblastic) and the Leydig cells. This subpopulation expressed all or some of these antigens according to their stage of differentiation; all cells are labelled by MY7 Mo Ab which is directed against myelomonocytic cells, including stem cell. Using monoclonal antibodies directed against more mature cells (MY4, MO1 and MO2), the number of labelled cells decreased in this mesenchymal population. MY4 Mo Ab, which detect myelomonocytic cells excluding stem cell, label fewer than MY7 Mo Ab. MO1 MO Ab and MO2 Mo Ab, respectively, directed against antigens of more mature or mature monocytic cells, label less number of mesenchymal cells, which are histiocytes after 20 weeks. These ultrastructural and immunohistochemical findings suggest that cells of the MPS differentiate within the interstitium.

Evidence of 3 beta-hydroxysteroid dehydrogenase activity in several murine embryonal carcinoma cell lines.

This report describes, for the first time to our knowledge, a possible steroidogenic activity in established murine embryonal carcinoma cell lines (PCC3, PCC4, F9), revealed by a 3 beta-hydroxysteroid dehydrogenase activity (revelation of NADH2 by staining, and RIA assessment of delta 4-androstenedione). The remarkable analogy between such totipotent cells and embryonal cells may suggest that this activity could be present before histologic organization of the embryonal testis. Nonmalignant embryonal cells such as fibroblasts (3/A/1/D-3) or myoblasts (T984) were also found to possess a 3 beta-hydroxysteroid dehydrogenase activity, thus suggesting that this enzyme is not specific to hormone-secreting cells, but the sign of a more general phenomenon.