  The vertebrate immune system is a wonder of modern evolution. Occasionally,
however, correlations within the immune system lead to inappropriate
recruitment of preexisting T cells against novel viral diseases. We present a
random energy theory for the correlations in the naive and memory T cell immune
responses. The non-linear susceptibility of the random energy model to
structural changes captures the correlations in the immune response to mutated
antigens. We show how the sequence-level diversity of the T cell repertoire
drives the dynamics of the immune response against mutated viral antigens.
