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Using a panel of antigens (actin, myosin, tubulin, albumin, transferrin, peroxidase, thyroglobulin, DNA, prolactin, TNP and myelin basic protein (MBP], we have tested the antibody activity of serum and cerebrospinal fluid (CSF) from healthy individuals, patients with multiple sclerosis (MS) and individuals with other neurological diseases. No differences in the concentrations and specificities of the serum antibodies were observed among the 3 groups. In contrast, we found that MS patients often had elevated CSF antibody levels against many antigens of the panel. The MS patients with local immunoglobulin production in the central nervous system (CNS) had the highest antibody levels. Restricted antibody activity against a given antigen of the panel was not observed. Compared to the two other groups, the MS group had equivalent titres of anti-MBP antibodies in the CSF. These results suggest that, in MS, a general immune dysregulation exists which leads to a local expansion of B lymphocytes producing autoantibodies with reactivities similar to those of serum natural autoantibodies.

Normal and viral-infected rainbow trout (RT) were tested for serum antibody activity against self and nonself antigens. Particularly high titres of anti-trinitrophenyl (TNP) antibodies were noted, as in other fish species. To analyse this, the anti-TNP antibodies were isolated by affinity chromatography and their capacity to interfere with viral infection in vitro was studied. We selected RT fibroblasts as target cells, and two common pathogenic viruses in trout, a rhabdovirus, viral haemorrhagic septicaemia virus (VHS) and a birnavirus, the infectious pancreatic necrosis virus (IPN). Anti-TNP antibodies were examined for their capacity to neutralize VHS and IPN viruses. Data obtained show that the anti-TNP antibodies, even at high concentrations, only partially neutralized virus. In contrast, when anti-TNP antibodies were assayed for their protective activity using RT fibroblast cells infected with VHS or IPN viruses, results showed high protective activity, regardless of serum origin or of the virus used, when the antibodies were added to the cell culture after viral infection. Therefore, our experiments indicate that the protective activity does not seem to be due to a direct interaction of the antibodies with the viruses. It is suggested that virus-modified cell surface self structures exhibit new epitopes which interact with the anti-TNP antibodies. Such an interaction would allow anti-TNP antibodies to participate in a non-specific defence mechanism against viral infection.

Twenty-six sera containing anti-HIV antibodies from individuals with AIDS, AIDS-related complex, lymphadenopathy syndrome, or from seropositive individuals without clinical symptoms, were tested for the presence of natural autoantibodies (NAb) to actin, DNA, tubulin, thyroglobulin, albumin, myosin and TNP-BSA. Sera from 22 seronegative individuals at high risk for HIV infection were also examined. NAb titres to all these antigens were found to be elevated in both groups as compared to the titres in pooled normal human sera. The most prevalent NAb were those of the IgG class directed against TNP found in high titre in seropositive individuals. On the basis of the above results, sera from 50 anti-HIV-positive and 67 anti-HIV-negative individuals were tested for IgG antibody activity against a panel of protein antigens with different degrees of TNP substitution. The greater the TNP substitution, the higher the titres of IgG antibodies detected in anti-HIV-positive sera. Antibody titres in seronegative individuals at high risk for HIV infection were independent of the degree of TNP substitution. In almost all cases, the highest titres of IgG anti-TNP antibodies were found in anti-HIV-positive sera from individuals with clinical manifestations.

Sera of BALB/c mice immunized with either trinitrophenyl (TNP) coupled to bovine serum albumin (TNP/BSA) and Freund's adjuvant or TNP/BSA and TNP coupled to mouse serum albumin (TNP/MSA) without adjuvant were tested for antibody activity against a panel of antigens: TNP/BSA, DNA, actin, myosin, tubulin and transferrin. Anti-DNA antibody activity in the serum increased significantly in immunized mice; this activity followed the increase in the anti-TNP titres. Sera from MRL/lpr/lpr autoimmune mice were also tested for antibody activity against a panel of antigens. Again, it was found that the level of the anti-TNP antibodies followed the level of anti-DNA antibodies. Purified antibodies isolated from both immunized BALB/c and MRL/lpr/lpr mice on a dinitrophenol(DNP)-lysine immunoadsorbent shared antibody activity against both TNP and DNA. The results obtained suggest that a single region in the antibody binding site is responsible for both anti-DNA and anti-TNP activities, that TNP-like groups may represent a "public epitope" carried by various antigens and that antibodies obtained after experimental immunization and antibodies appearing in autoimmunopathological situations apparently possess similar specificities.