Immune complexes in humoral immune responses: suppressive and enhancing effects

One explanation for F1 antiparent responses

The phenomenon of hybrid resistance, in which F1 offspring reject parental grafts, remains a perplexing problem. Here, Tina Dalianis and Lars Ahrlund-Richter propose that one component of the F1 antiparent response results from competition between the two sets of parentally derived major histocompatibility complex (MHC) molecules for 'promiscuous' peptides. Lack of tolerance in the F1 animal results from insufficient presentation of these peptides on the MHC molecule that has lower affinity for the peptides.

Circulating immune complexes in experimental syphilis and their relation to immunological response against Treponema pallidum

It was found that circulating immune complexes (CIC) were formed in rabbits at different times after infection with Treponema pallidum. The CIC which appeared at the beginning of the disease were short-lived (2-6 weeks) but those appearing later than 20 weeks after infection remained for 10-25 weeks. CIC contained both IgM and IgG classes of immunoglobulin. The antibodies present in CIC were found to be specific and nonspecific for T. pallidum. The presence of CIC led to a marked decline of treponemal antibodies in rabbit sera. The cell-mediated immune response measured by the macrophage migration inhibition (MMI) test at the beginning of the disease (up to 12 weeks) was not decreased. However, when syphilis lasted for more than 14 weeks and when CIC were formed mainly from IgG, a distinct decrease in the ability of lymphocytes to cause MMI was observed. These findings strongly suggest that IgG-complexes suppress the immunological responsiveness of lymphocytes against T. pallidum which in turn facilitates the multiplication of treponemes in the host.

Immune complex assays: diagnostic and clinical application

The presence of circulating immune complexes have been described in many different human disease states but the significance of their presence has always been a subject for debate. Improvements in the methods of detecting immune complexes have demonstrated a wide degree of heterogeneity, which accounts for the difficulty in obtaining accurate and reproducible measurements, even in the same individual. Techniques for isolating individual complexes, characterizing their pathophysiological properties, and biochemically analyzing the nature of the complexed antigen are now being used to provide data that is helping to clarify the role of immune complexes in the pathogenesis of disease. In addition, such studies are also providing data which is proving that immune complexes have a potential role in immune regulation.

Cellular and humoral immune responses in experimental aspergillosis in mice

Invasive aspergillosis was established in a naive murine model. Both humoral and cellular aspects of the immunological mechanism responded to invasion. Circulating immune complexes containing IgG in the infected group of animals were detected by both the C1q and conglutinin solid phase assays. Attempts to identify these complexes as Aspergillus antigen-specific complexes were unsuccessful. Cellular responses, as measured by blastogenic activity and inhibition of migration of sensitized cells were significantly elevated in the infected group.

NK-patterned binding expressed by non-NK mouse leukocytes

Previous studies demonstrated that NK-cell-enriched spleen cells bind to sensitive but not to resistant mouse lymphoma targets, measured by a single-cell target binding assay. In the present report we further analyzed this "NK-patterned" binding using effector cells with high, low or no NK activity. In agreement with previous results, nylon-wool-passed spleen cells as well as a cloned cytotoxic cell line with NK activity bound tumor targets largely according to their NK sensitivity; NK-sensitive tumors had a higher frequency of binders than the more resistant ones. The correlation coefficient relating the percentage target binding cells (TBC) for each tumor with the ability of the same tumor to inhibit lysis in cold target competition assays was consistently higher than that relating percentage TBC with direct NK lysis. A non-lytic variant of the cloned cytotoxic cell line had a binding pattern identical to that of the lytic line, demonstrating that "NK-patterned" binding occurred in the absence of lysis. Thymocytes, which are totally devoid of NK activity, also bound preferentially NK-sensitive targets, and their binding was decreased after trypsin treatment or in the presence of EDTA. Peritoneal macrophages also showed "NK-patterned" binding, thus demonstrating that this was not restricted to cells in the T-cell lineage. Variants from a mouse lymphoma selected for decreased NK sensitivity bound a lower frequency of NK-active (nylon-wool-passed spleen cells) and inactive cells (thymocytes, peritoneal macrophages). This study therefore showed that the membrane property conferring NK-binding selectivity exists on several types of non-NK leukocytes.

HLA and renal transplantation: yet another approach

Renal allografts obtained from living related donors have considerably better chances of success than allografts from cadavers. The genetic factors that influence graft survival are linked to the HLA gene complex. Although results of cadaver transplants have not improved significantly when donor and recipient are matched for HLA-A and -B antigens, accumulating data suggest that matching for the more recently recognised HLA-DR antigens may produce increased graft survival.

Role of circulating immune complexes in renal diseases

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