Immunological communications最新文献

The protein A-binding site of human IgM was studied by affinity chromatography on SpA-Sepharose using fragments derived from a human monoclonal SpA-reactive IgM, Iz. Neither Fabmu nor (Fc) 5mu fragments were retained on the column but IgM reactivity was unaffected by thermic treatment during proteolysis. Products intermediate between IgM and (Fc) 5mu fragments produced during shorter proteolysis showed a reactivity related to their content in Fabmu regions. On the other hand mild reduction of IgM Iz to monomeric subunits results in a dramatic loss of SpA-affinity. However these subunits, like F(ab') 2mu but unlike Fab'mu fragments, showed a significant interaction with the column. Thus, the principal requirement for SpA reactivity with IgM Iz seems to be related to the presence of Fabmu regions in a polymeric state resembling native IgM.

The effect of alpha 2HS glycoprotein on lymphocyte reactivity to phytohemagglutinin (PHA) was investigated. The results show that alpha 2HS glycoprotein, rather than enhancing lymphocyte reactivity to PHA as suggested by earlier correlation studies, inhibits such reactivity. Experiments suggest that this inhibition is unlikely to be the result of alpha 2HS glycoprotein binding either PHA or 3H-thymidine but is more likely to act at the cellular level.

We have previously reported that a mammary tissue-specific antigen (MTA) occurs in the circulation of rats bearing the metastatic mammary tumor, TMT-081. In this communication we present immunochemical evidence that MTA also exists in the form of a soluble immune complex in the sera and ascites of TMT-081-bearing rats. This immune complex, however, has no effect on the growth of TMT-081 in rats. Neither the MTA nor the immune complex could be detected in the circulation of lactating rats or rats bearing the nonmetastatic mammary tumor, MT-100. Thus, it appears that the spontaneously metastasizing tumor, TMT-100, considered previously to be nonimmunogenic or weakly immunogenic by conventional tests, does in fact elicit an apparently ineffective humoral response as manifested by the formation of an immune complex containing MTA.

Serological interactions among sera of human renal graft recipients in double diffusion in gel were observed by chance. Antigen was detected in six of 127 recipients and antibody in two of 30 recipients tested. One of the six recipients carrying the antigen had also antibody in one serum sample. On the basis of the pattern of reactions observed, the hypothesis was expressed that the described antigen-antibody system had "pan" rather than "allo" character.

Recently, by using a comprehensive synthetic strategy developed in this laboratory, we localized four sites (T sites) within the polypeptide chain of lysozyme recognized by T cells from two high responder mouse strains, DBA/1 and B10.BR. However, to detect minor specificities, the selective enrichment of lysozyme reactive cells, would be required. T cells from long-term cultures maintained by repeated stimulation with antigen are selectively enriched for that antigen. It is not known whether maintaining T cells for extended periods of time in vitro has any consequences on the profile of T cell recognition. In the present study, T cells from long-term cultures, derived from these two high responder lysozyme-primed mouse strains, were examined for their responsiveness to a series of synthetic overlapping peptides encompassing the entire polypeptide chain of the lysozyme molecule. We have found that the profile of T cell recognition of the long-term cultures may not reflect that of the lysozyme primed lymph node cells, but that it is subject to a shift in specificity towards submolecular features of the molecule. In addition, we have identified in B10.BR mice another region within the polypeptide chain of lysozyme (residues 72-84) which may potentially harbor a previously undetected (in lymph node cells) minor T site.

A clinical laboratory carrying out tests for antinuclear antibodies requires an efficient, reliable preparation method to produce a high yield of nuclear antigens at low cost and a very sensitive, specific assay method for antigen activity. Various tissues were employed for preparation of small nuclear ribonucleoprotein (snRNP) and Sm antigens for these purposes. Fresh calf thymus cells and nuclei, commercially available calf and rabbit thymus acetone powders, fresh rat kidney and liver cells were used as sources of antigens prepared similarly by methods published previously. Preparations of antigens from whole calf thymus cell extracts were prepared with and without inhibitors to protease and RNase. snRNP and Sm antigens were assayed at each preparation step by hemagglutination inhibition (HAI). Using HAI it was possible to routinely assay snRNP and Sm at nanogram/ml quantities which was 10(6) fold more sensitive than Ouchterlony immunodiffusion. Results were expressed as relative specific activity as compared with calf thymus nuclear extract prepared by conventional methods. Protease and RNase inhibitors did not significantly increase yields. Thymus was the best source of snRNP and Sm. Fresh calf thymus extract produced a good, stable, reliable quantity of antigens, whereas calf and rabbit thymus acetone powders provided antigen at higher specific activity with less labor but slightly lower yields. Thus, considering the total cost of preparations, commercial sources may be superior to fresh sources in the clinical laboratory setting. These studies also revealed the utility of the sensitive HAI test not only in the clinical laboratory but also for further research endeavors.

The ion permeability of lipid membranes formed on Millipore and Nuclepore filters has been found to exhibit stepwise reductions in electrical resistance in the presence of Forssman antigen, appropriate antiserum and complement. The results appear to support the "hydrophobic doughnut" or transmembrane channel hypothesis, which envisions several polypeptide chains anchoring from more than one terminal complement component to interact with one another within the lipid bilayer. Channel formation in these artificial membranes is believed to be due to the insertion of complement proteins. Concentrations and temperature studies were carried out to ascertain that the electrical responses were owing to the generation of stable channels by complement across the membrane. The diameter of these channels was estimated to be in the order of 100 A.

Intravenous inoculations of purified Protein A of Staphylococcus aureus Cowan I cause significant (p less than 0.01) regression of di-methyl-benz-anthracene (DMBA)-induced mammary adenocarcinomas in Sprague-Dawley rats. Direct tumor cell counts of treated tumors showed fewer (p less than 0.005) viable tumor cells than did tumors from untreated controls. Plasma immunoglobulin G concentration showed a significant (p less than 0.05) increase compared to that of controls. However, the concentration of immune complexes and percentages of T-rosettes did not change. Peripheral blood mononuclear cells (PBMNC) from treated animals showed increased cytotoxicity (p less than 0.005) compared to that of controls. Plasma of treated animals potentiated PBMNC cytotoxicity (p less than 0.05) and showed increased antibody and complement-mediated cytotoxicity (p less than 0.025). The exact mechanism of protein A-induced potentiation of anti-tumor immune reactivities leading to tumoricidal response is not known. However, our data are suggestive of the involvement of both cellular and humoral immunity of the host in the tumor regressive phenomenon.

The effect of glutaurine, a newly discovered parathyroid substance, on human NK cell activity and on lymphocyte markers was studied. Both in vivo and in vitro treatment with glutaurine markedly enhanced the depressed natural lymphocytotoxicity of tumor patients without influencing their lymphocyte subpopulations. On the other hand it had no effect on the NK cell activity of healthy lymphocytes and of tumor patients' lymphocytes with originally "normal" NK activity. The NK-enhancing effect of glutaurine could not be explained by augmentation of the number of potential effector cells. It is suggested that glutaurine increases the originally low spontaneous killer activity of tumor patients' lymphocytes through an indirect regulatory mechanism.