Pemphigus vulgaris is a cutaneous autoimmune disease in which the occurrence of autoantibodies directed against desmoglein-3 and other self-antigens has been well established in patient sera. However, V-region interactions (connectivity) of serum IgG and IgM have not been analysed to date. In this report, it has been demonstrated that IgG and IgM in the sera of pemphigus vulgaris patients bind a preparation of F(ab')2 fragments fractionated according to their isoelectric points, and that a pattern of connectivity distinguishable from that of healthy donor sera arises when the sera are tested against 20 individual isoelectric-focusing-separated F(ab')2-containing fractions. This suggests that there are alterations in regulatory networks. In spite of the fact that prednisolone-based treatment of pemphigus patients has proved to be effective in controlling the disease, some undesirable effects associated with this form of treatment have prompted investigation into other therapeutic approaches. One possible approach to the treatment of this autoimmune disease is the use of high doses of normal polyclonal immunoglobulins. In fact there are a few reports of the empirical intravenous administration of immunoglobulins to pemphigus vulgaris patients. The results presented here provide the rational basis for using such a treatment, since it is demonstrated that a deviation from healthy V-region interactions can be attributed to pemphigus patients and that such a condition is considered to be modified by this type of immunotherapy.

Following primary infection with human immunodeficiency virus (HIV)-1, antibodies against specific HIV-1 epitopes are elicited. However, non-HIV-1 specific antibodies, including autoantibodies, also arise. In fact, it has been proposed that such autoantibodies have an important role in the pathogenesis of HIV-1 infection. Because an imbalance in connectivity has been associated with autoimmune processes, we investigated the connectivity status of HIV-1-infected individuals. Moreover, we tested the possible role of viral load and CD4(+) T-cell counts, in connectivity, because these parameters appear to be important in the prognosis of HIV-1 infection. Results show that indeed, there is an alteration in connectivity in these patients, both for immunoglobulin (Ig)G and IgM, which is an immune alteration not previously identified in HIV-1 infection. In addition, our results show that viral load and CD4(+) T-cell counts are both equally important in defining the characteristic pattern of connectivity in HIV-1-infected individuals, and that neither is independently responsible for alterations in patient connectivity status.

Connectivity, the self-defined interactions between antigen-recognising molecules in a network system can in part be assessed by measuring the reactivity of a given serum against an ordered set of immunoglobulin (Ig)G F(ab 0 ) 2 fractions, separated by means of isoelectric focusing so that, the serum reactivity against the whole set of fractions defines a characteristic pattern of connectivity. Deviations from the normal condition (healthy donors) have so far been documented for two autoimmune diseases: systemic lupus erythematosus (SLE) and pemphigus vulgaris, as well as for human immundeficiency virus (HIV)-1 infection. We tested here if bacterial infections lead to alterations in connectivity. In addition, we wanted to test if two antigenically related bacteria would produce similar or otherwise distinctive connectivity patterns. Connectivity analysis was applied on the sera from tuberculosis and leprosy patients and the sera from healthy donors were used as control. No statistically significant differences between the three groups studied were found. These results have implications for theories that set the origin of autoimmune diseases in microbial infections. To the best of our knowledge, this is the first attempt to analyze the connectivity status in bacterial infections.