We have compared the levels of immunoglobulins G (IgG) and G4 (IgG4) in extreme seropositive patients from the GRIV cohort consisting of 168 patients with slow progression (SP) and 60 with rapid progression (RP) as well as in 173 healthy controls. IgG levels were significantly higher in SP patients than in RP patients (P = 0.008), both higher than in seronegative individuals. IgG4 levels were significantly lower in SP patients than in RP patients (P = 0.001), both lower than in seronegative individuals. We tried to correlate these levels with biological parameters (CD4⁺ and CD8⁺ cells, total lymphocytes, white blood cell counts, percentage of CD4⁺ cells, and viral load) as well as with genetic markers from Th1/Th2 cytokines (IL2, IL4, IL6, IL10, IL13, and IFNγ). IgG levels were correlated with the percentage of CD4⁺ cells in SP while IgG4 levels were correlated with CD8⁺ cell count in SP and with percentage of CD4⁺ cells in RP patients. Among the parameters measured in SP patients at the time of inclusion in the study, the best predictor of progression towards AIDS was the viral load, the best predictor for stability was CD4⁺ cell count, but overall, the best predictor for SP evolution (stability vs. progression) appeared to be the percentage of CD4⁺ cells. Interestingly, correlations between the levels of IgG or IgG4 and the cytokine gene polymorphisms were found, notably in the IL10 gene.