ABSTRACT: The immunosuppressive activity of fractionated human seminal plasma (SP) was investigated both in vitro (on human lymphocytes) and in vivo with Balb/ c mice. SP fractionation by dialysis allowed delineation of the major suppressor factors according to their respective sizes—small (< 12kD) or large (> 12kD). In vitro, large molecules were found to suppress the B‐cell proliferative response induced by the Nocardia mitogen, while small molecules suppressed the T‐cell proliferation induced by phytohemagglutinin. In vivo, immunosuppression was obtained almost exclusively on T‐independent responses after preliminary treatments either with unfractionated SP or with large SP molecules. Both type 1 and type 2 T‐independent responses were suppressed, as evidenced by plaque‐forming cells and antibody assays. In contrast, no immunosuppression was found in vivo after treatment by small SP molecules. Purification of the B‐cell suppressor by gel filtration and high‐performance liquid chromatography, as well as by preparative isofocusing, indicated that its molecular weight was 180 kD and its isoelectric charge was between pH 5 and 6. This factor is a protein, as evidenced by pronase digestion. A possible role for this molecule in the protection of sperm against the female immune system is discussed.
A T-suppressor (TS) lymphokine was purified from the supernatant of a T hybridoma established from CD3+ CD8+ CD57+ lymphocytes of a healthy bone marrow transplant patient. Using polyclonal rabbit antibodies, raised against a TS-enriched preparation, a specific protein of 47,000 MW was identified, which was used to prepare monoclonal antibodies. The screening of hybridomas was carried out by strip-ELISA, in which the 47,000 MW band, transferred on a membrane, served as antigen. One of these monoclonal antibodies (IgM kappa) was selected for purification of the native TS molecule, which exhibited the high suppressive activity on the phytohaemagglutinin (PHA) and alloantigen responses of peripheral blood lymphocytes. The establishment of amino acid sequences of five trypsinized cleavage peptides confirmed that this protein has not been previously identified. This lymphokine--also detected in the supernatant of normal CD8+ CD57+ lymphocytes--is likely involved in bone marrow transplantation tolerance.
ABSTRACT: The nature of the human semen T‐sup‐pressor was investigated in vitro on human lymphocyte proliferations induced by phytohemagglutinin (PHA) or by alloantigens. Purification by ion‐exchange chromatography, followed by butanol extraction, showed this factor to be present only in the polyamine‐containing fractions. The purified product, obtained by preparative thin‐layer electrophoresis, contained almost exclusively spermine and exhibited the same suppressive activity as this polyamine. Human T‐lymphocyte suppression occurred in the presence of fetal calf serum, but it did not occur in a serum‐free medium. No suppression was observed after preincubation of the fetal calf serum with hydroxylamine, a spermine oxidase inhibitor, whereas a nondialyzable fraction, from normal human serum, decreased the suppression. The semen factor did not act by direct cytotoxicity, as there was no effect of preincubation and suppression could be induced only within the first 6 hr of mitogen activation. These data demonstrate that the in vitro T‐suppressive activity of semen can be assigned mainly to spermine and show that in vivo this suppression must require locally the presence of a spermine oxidase or related enzyme.
To improve the mucosal antibody response against a short amino acid (aa) sequence (ELDKWA) of HIV gp41, we have investigated a construction including this peptide in‐line with the Pan DR epitope (PADRE). ELDKWA is a conserved peptide playing a key role in the pathogenicity of HIV transmission. PADRE is a non‐natural peptide with multipotential immunogenic properties. The results show striking differences between mucosal and systemic immune systems, with a preferential response of the mucosal organs. In contrast with most mucosal immunizations, the intracellular response persists for over two months after the last injection. This strongly suggests that further investigations of conserved key epitopes from various pathogens may lead to safe and chemically defined mucosal vaccines with synthetic peptides. These candidate vaccines with free peptides may be suitable for mass campaigns even in developing countries.
A hepatitis B virus (HBV) binding factor (HBV-BF) was identified in normal human serum interacting with the pre-S1 and pre-S2 epitopes of the viral envelope located within the protein domains involved in recognition of hepatocyte receptor(s). This molecule was characterized as a 50-kDa glycoprotein showing an isoelectric point of 7.13 with a biological activity depending on its native molecular conformation and on intact sulfhydryl bonds. Monoclonal antibodies to HBV-BF recognized a membrane component of the normal human liver whereas they were unreactive with hepatocyte membranes of other species and with those of the HepG2 cell line. These results suggest that the HBV-BF represents a soluble fragment of the membrane component and can be related to the HBV receptor mediating attachment of HBV to human liver cells.
ABSTRACT: The in vitro suppressive activity of spermine to PHA‐induced proliferation of human T lymphocytes is shown to be abolished by normal human serum. This protection acts within the first 4 hr of culture and is due to a protein of 67 kDa, showing an isoelectric charge of pH 4.9. This protein does not bind, or modify, spermine and does not inhibit spermine oxidase activity, an enzyme required for the in vitro suppression. Results with acrolein confirm that this eventual cleavage product is probably not involved in the spermine‐induced suppression. Nevertheless, since serum also reduces acrolein‐induced suppression, it is probable that both these protective mechanisms are related. Such a protection of T lymphocytes by a serum factor may play an important role by preventing diffusion, outside the genital tract area, of a potential spermine‐induced immunosuppression.
