CD40LG and infection: This reactivation was accompanied by a robust and specific IgG antibody response, without detectable IgM antibodies, similar to the humoral response associated with Brill-Zinsser disease [16], [17], [19], [20], and pulmonary lesions similar to, but generally less extensive than the lesions observed in the lungs of mice following primary infection with R. prowazekii[24].