The fine specificity and cytokine profile of T-helper cells responsive to the alpha3 chain of type IV collagen in Goodpasture’s disease

Goodpasture's disease is a severe nephritis characterized by autoantibodies to the alpha3 chain of type IV collagen, alpha3(IV)NC1, in the glomerular basement membrane. The disease is very strongly associated with HLA-DR15, the affinities of alpha3(IV)NC1 peptides for DR15 are known, and elution experiments have identified major naturally processed sequences. Here, the fine specificity and cytokine profile of alpha3(IV)NC1-reactive T cells from patients with Goodpasture's disease is defined. Peripheral blood mononuclear cells from patients at diagnosis proliferated in response to significantly more peptides (chi(2) = 8.6, P = 0.004) from a panel spanning the sequence of alpha3(IV)NC1 than did those from control DR15-positive donors and were highly focused (P = 0.0002, binomial distribution) on two peptides, alpha3(71-90) and alpha3(131-150). Some peptides induced interferon-gamma, but none induced IL-4. Resolution of disease was accompanied by a striking deviation of the responses from proliferation to secretion of the T-regulatory cytokine IL-10, and addition of neutralizing antibody confirmed that such IL-10 production was suppressive. The affinity of the peptides for DR15 molecules was positively correlated (chi(2) = 14.6, P = 0.00067) with the ability to elicit proliferation. However, unlike foreign antigens, this hierarchy is not due to responses against the major naturally processed peptides, which rarely stimulated proliferation and which have only intermediate affinity for DR15 molecules. It is inferred that the helper response to alpha3(IV)NC1 in Goodpasture's disease is dominated by epitopes that are normally inefficiently presented because of processing constraints.