Consistent with the observed effects of defective germinal center function or robust T-cell dependent immunization on VH usage in CLL, PCA of a gene signature comprised of 148 genes differentially expressed between VH11 and non-VH11 CLL revealed that VH11 and non-VH11 CLL clustered with BCR-stimulated and anti-CD40-stimulated B cells, respectively. The gene discussed is CD40; the disease is B-cell chronic lymphocytic leukemia.