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The distribution of phenotypes of the group specific component (Gc) was examined in 85 AIDS patients and in 40 couples, each consisting of one HIV seropositive patient and one seronegative sexual partner. Phenotype and allele frequencies in these groups did not differ significantly from those in a Swedish control population. Our observations did not indicate any involvement of the Gc system in susceptibility to HIV infection or progression to AIDS.

Antibodies to soluble ribonucleoprotein (sRNP) are by definition a prerequisite for the diagnosis mixed connective tissue disease (MCTD). They are also found in 30--40% of other rheumatic conditions with a high titred speckled IFL reaction. The same is true for the most characteristic clinical features of MCTD, viz. Raynaud's syndrome and polymyositis--polymyalgia. The serological and clinical symptoms mentioned are closely associated. An association between anti-Sm and the SLE symptoms butterfly erythema, nephropathia, other visceropathias and cerebrovascular disease is confirmed by the present study. Although anti-Sm has less diagnostic specificity for SLE than has anti-ds-DNA, it is useful as a diagnostic aid in SLE cases lacking the latter antibody. The results of the present study tend to support the hypothesis that anti-sRNP may be associated with a prophylactive effect against serious vasculitis and nephropathia. When anti-sRNP and anti-Sm occur together they seem to act competitively so that the symptom associated with the antibody having the highest titre tends to dominate the clinical picture. Both anti-sRNP and anti-Sm produce speckled nuclear patterns in the indirect immunofluorescence test. Sera with immunofluorescence titres below 1/25 were not found to react against either sRNP or Sm. On the other hand all sera tested that had a speckled IFL reaction greater than or equal to 1/800 also had anti-sRNP.

Previous studies have shown that the small-bowel shunt operation for morbid obesity may be followed by signs of enhanced cell-mediated immunity and polymorphonuclear (PMN) granulocyte bactericidal capacity. In the present study seven patients, operated 4 months--4.5 years previously and exhibiting postoperative arthralgias, arthritis, and/or skin rashes, were investigated with regard to their PMN adherence and bactericidal capacity and plasma levels of complement factors 3 and 4 (C3 and C4). There patients showed a decreased PMN bactericidal capacity compared both with 10 other shunt-operated patients without skin and joint symptoms and with healthy controls, whereas PMN adherence was lower than for the non-symptomatic patients but similar to that of the controls. Two patients had C3 levels above the reference value; all had normal C4 values. Thus, a small-bowel shunt operation for obesity, complicated by skin and joint symptoms, might be associated with decreased PMN bactericidal capacity.

Isolated IgM RF inhibited the IgG-induced release of lysosomal substances, measured as 'large molecular size vitamin B12-binding protein' (LBP) and beta-glucronidase, from separated human granulocytes. The effect was most marked when cytochalasin B was added to the experimental system. The results indicate that the RFs interact with the granulocyte binding region of IgG.

The ability of isolated IgG and F(ab)2 fragments to agglutinate IgG-coated latex particles was used as a test of IgG-RF activity. No definite differences could be proved between controls and RF-negative RA patients, whereas the latex titres of IgG and F(ab)2 of sero-positive RA patients were higher. The IgG latex activity was recovered in the fractions between the 19S and 7S after gradient centrifugation of serum or isolated IgG at pH 7.2 and within the 7S fraction after centrifugation at pH 4.1. The dissociated IgG complexes reformed after neutralization, thus indicating a self-association of the IgG molecules.

The reactions of sera from patients with connective tissue disease with Chrithidia lucillae kinetoplasts were examined with the indirect immunofluorescence technique on untreated smears and smears pretreated with DNAse, RNAse or trypsin. Of 28 completely examined reacting sera, 20 had their reactions inactivated by DNAse alone, two by DNAse and trypsin, and 6 by DNAse and RNAse. This suggests that although the Chrithidia test is probably at present the method of choice for the diagnostic demonstration of DNA antibodies, its results are not completely unambigous. The kinetoplast DNA is probably conjugated to a non-histone protein and antibodies to the conjugate may occur in some instances. In other instances, antibodies may be directed against DNA-RNA complexes. If the Chrithidia kinetoplasts contain a protein moiety, the latter is apparently not identical with the protein contained in the Chrithidian cell nuclei.