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The sera from 34 patients with malignant melanoma at various clinical stages of the disease were examined for the presence of circulating immune complexes (CIC) by the C1q solid-phase assay. Their urine and serum samples had been previously examined for the presence of an urinary melanoma-specific protein (MSP) and the corresponding serum antibody. Low levels of CIC (only in the third stage of the disease) and no positive correlation with the presence of MSP were found. The discordance between our and other author's data stresses again the fact that the different laboratory methods for CIC evaluation reveal in a different way the various CIC populations occurring in several diseases.

Immunoglobulins, C3 and C4 levels and circulating immune complexes have been measured on admission sera from 34 children admitted to a Naples hospital during the winter of 1978/79 with severe, usually fatal, acute respiratory infections and in age-matched controls from Rome. The Naples sera were characterised by low IgA, C3, and C4 levels, increased IgM and IgG concentrations, and high titres of circulating immune complexes. These immunological abnormalities could explain the high concentration of fatal cases.

Sixty-three sera of patients with leprosy were tested for the presence of circulating immune complexes (CIC) by C1q solid phase assay (C1qSPA). The mean values in CIC levels in leprosy patients were very high in comparison to native and European controls. No difference was found in the tuberculoid and lepromatous forms, but there was a good correlation between the presence of CIC and autoantibodies.

Pathological (190) and normal (33) sera were tested for their content of circulating immune complexes (CIC) by a battery of 13 assays performed in 11 laboratories. Statistical processing was done both by pooling all pathological samples and by extracting those falling into well-defined disease groups, i.e., rheumatoid arthritis, diabetes, lupus, melanoma, and glomerulonephritis. Highly significant correlations between methods--taken two at a time--for each disease differed in proportion (ranging from 6 to 30%) and in the pattern displayed on a checkerboard. Disease-linked patterns were also found when a function maximizing discrimination between pathological and normal samples was derived by combining the information from all methods. Here the order and the weight attributed by the computer to the methods differed for each of the disease groups. Taken together these results are interpreted as an indication that all assays may not determine the same classes of CIC, and thus vary in sensitivity depending on the prevailing properties of the complexes present in the serum, which in turn may depend on the etiology, pathogenesis, and stage of the disease.

The polyethylenglycol (PEG) precipitation technique has been employed for the measurement of immune complexes in the circulation of 100 normal subjects and in 14 patients suffering from a variety of diseases (systemic lupus erythematodes, nephrosic syndrome, cryoglobulinaemia, Buckley's syndrome). Values higher than 0.80 UA on the absorption scale were considered pathological, namely 2 standard deviations above the mean (0.32 UA) in the subjects examined; in the patients, values between a minimum of 0.98 UA and a maximum of 2.38 UA were observed. Longitudinal study of these cases also pointed to the disappearance of immune complexes during therapy. The results suggest that the PEG precipitation technique can play an important part as a screening test in situations in which circulating IC pathology is suspected; it is also a sensitive means of monitoring treatment.

The polyethylene-glycol (PEG) precipitation assay was used to examine the sera of sixty-nine pregnant women, thirty with normal pregnancies, ten with toxaemia of pregnancy, eleven with pregnancy complicated by diabetes and eighteen with case histories of recurrent abortions in order to find evidence of eventual circulating immune complexes (CIC). CIC were not seen in normal pregnancies, but were found in two of the toxaemic group, in two of those with recurrent abortions and in two of those with diabetes. After delivery, these six positive cases were all negative. The presence of CIC may have a determining role in the pathogenesis of some of the cases of the above conditions.

Thirty sera from eight patients with disseminated or localized hydatid disease have been examined for the presence of circulating immune complexes (CICs) by the conglutinin-binding assay and for immunoglobulin levels. The highest levels of CICs were of the immunoglobulin A (IgA) class, with lower values of IgG-CIC and IgM-CIC; these results did not correlate, except for IgG, with the free immunoglobulin levels. Efforts to identify parasitic antigen(s) involved in the CIC formation with different methods have been unsuccessful. In the follow-up of each patient, CIC appeared to be better correlated to clinical conditions than to hemagglutination titers. We have concluded that the presence of CIC in hydatid disease is probably an expression of B-cell polyclonal activation and that these complexes are valuable in the clinical monitoring of the disease.

A modification of the conglutinin-binding assay has been used for antigen identification in circulating immune complexes (IC). The complexed antigen was identified, in conglutinin-bound complexes, by antibodies or antibody fragments, specifically directed against the antigen. These antibody preparations were either radiolabelled or detected with 125I-protein A. This system was found efficient using in vitro-formed bovine serum albumin--anti-bovine serum albumin and tetanus toxoid--anti-tetanus toxoid soluble immune complexes at equivalence or at slight antigen or antibody excess. In addition, with 125I-IgG--anti-HBs and with 125I-F(ab')2--anti-HBs, we examined 44 sera from 41 patients with viral type B hepatitis and the presence of HBs was observed in 18 (40.9%) IC containing tested samples. Therefore, this method appears applicable to clinical investigation.

Using an ultracentrifugation technique human immunosuppressive virus (HIV) (GP15 and GP41), anti-HIV (anti-GP15 and anti-GP41) immune complexes were detected in the sera of 3 (1 Acquired immune deficiency syndrome (AIDS), 1 AIDS related complex (ARC), 1 Lymphadenopathy syndrome (LAS] out of 6 patients studied. Evidence for presence of HIV immune complexes was provided by: 1) demonstration of GP15 anti-GP15 and GP41 anti-GP41 immune complexes at neutral pH (pH 7.2); and 2) presence of free HIV antigen and specific HIV antibodies after dissociation of immune complex-like material with acid buffer. Formation of specific immune complexes in the sera of AIDS and ARC patients may be responsible for failure to detect free HIV antibodies in some of these patients.

The complement system was examined in a group of eight patients (six with lymphoadenopathy syndrome (LAS); two with acquired immunodeficiency syndrome (AIDS)-related complex (ARC], who were found to be human immunodeficiency virus (HIV)-positive, for the presence of specific HIV-anti-HIV complexes. A significant impairment of the classical and/or alternative pathway was found associated with the presence of cleavage fragments of C3 and/or B and a significant reduction in the complement factors studied. Ultracentrifugation fractions of serum samples obtained from one of the patients were assessed for the detection of specific HIV-anti-HIV (GP41-anti-GP41) complexes and were incubated with normal human serum to determine their complement activation capacity. A clear complement activation was found with the fraction in which a clear peak of HIV-anti-HIV (GP41-anti-GP41) immune complexes was present. The results demonstrate that specific immune complexes and complement activation are sometimes concomitantly present in patients with AIDS-related disease and that specific immune complexes may be one of the causal factors of the pathogenesis of complement activation in these patients. Possible consequences for the severe immune regulation with relevance to the dramatic failure in treating the virus effectively are discussed.

Eighty-seven seropositive subjects with HIV (human immunodeficiency virus) infection together with 20 normal controls with no history of any illness were investigated for the presence of circulating immune complexes (CIC) by the conglutinin binding assay (KgBA) and further studied for isotype characterization of CIC. Six out of 87 patients showing very high values for immune complexes (CIC) were studied for the presence of free antigen. In 3 out of 6 (1, IVc1; 1, III; 1, IVa) we could detect by ultracentrifugation analysis the presence of specific HIV (p15) anti-HIV (anti-p15) and gp41-anti-gp41 CIC. Evidence in favour of this finding is supported by: the presence of specific CIC (p15-anti-p15 or gp41-anti-gp41) seen only at pH 7.2; the apparent presence of free antigen and specific HIV antibodies were only at pH 4.0. The relevance of this finding lies in the attempt to explain the occurrence of false seronegativity seen occasionally in symptomatic patients. Thus, the presence of CIC might perhaps interfere in the routine assay (i.e. ELISA) making the diagnosis difficult. All these considerations will have to be taken into account in the future handling of this disease.

The polyethylene-glicol (P.E.G.) precipitation assay was used to examine the sera of 91 pregnant women, 30 with normal pregnancies, 16 with EPH-Gestosis, 20 with pregnancy complicated by diabetes and 25 with case histories of recurrent abortions, in order to find evidence of eventual circulating immune complexes (C.I.C.). We also examined 30 amniotic fluids from normal pregnant women and 6 from pregnant women with diabetes. Several sera and all amniotic fluids were also examined by rheumatoid factor (RF) - inhibition test. C.I.C. were not discovered in the normal pregnant women neither in their sera nor in their amniotic fluids, while they were found in the following cases: in 8 patients with EPH-Gestosis (50%), in 8 with diabetes (40%) and in 3 with anamnesis positive for recurrent abortions (12%). The 6 amniotic fluid samples from women with diabetes were all negative. We were only able to examine 11 of the 19 positive cases from 4 days to 5 months after delivery and C.I.C. were absent in the sera of all the patients.

Fifty-three sera from 29 patients with hydatid disease, all but one positive for specific anti-parasite antibodies and all negative for specific circulating antigens, were studied for the presence of circulating immune complexes (CIC) by conglutinin binding-assay (KgBA). Fourteen serum samples (26%) from eight patients (27%) were positive. These positive sera were pooled for each patient and the eight samples were PEG-precipitated and analysed for the presence of specific Echinococcus granulosus antigens in the CIC using a human anti-human-hydatid cyst fluid antiserum capable of recognizing the major antigenic systems of the parasite namely, antigens 4 and 5. The assays utilized for detecting antigen in CIC were: (a) blotting on nitrocellulose paper after sodium dodecil sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and specific immunological detection; (b) ultracentrifugation in acid buffer and subsequent detection of antigens by a sandwich-radioimmuno assay (RIA); (c) protein separation by isoelectric focusing (IEF) and specific immunological recognition. In addition, all positive sera were analysed for the presence of antigen in the CIC by a modified KgBA and by polyethylenglicol (PEG)-precipitation in acid buffer followed by immunological recognition of antigen. All tests gave negative results with the patients' samples, but were positive with preformed in vitro complexes between parasite antigens and corresponding antibodies. Failure to detect antigen in the CIC could be due to: 1) insufficient sensitivity of the assays used to detect hydatid antigens in CIC; 2) rapid clearance of antigen or CIC from the circulation; 3) presence of parasite antigen not recognized by the antiserum employed; 4) production of CIC as a result of polyclonal B-cell activation. This last hypothesis is supported by the demonstration of IgM-rheumatoid factor (RF) and anti-F(ab')2 antibodies respectively in 11 (44%) and 13 (52%) out of 25 patients.