Response: Lymphocyte counts prior to Hodgkin lymphoma development

In a recent issue of Blood, Clifford and colleagues 1 reported interesting findings from the Swiss HIV Cohort Study pertaining to the debated relationship, in the setting of HIV infection, between occurrence of Hodgkin lymphoma (HL) and degree of immune suppression. In contrast to previous data from the United States, 2 they found that HL risk did tend to increase with lowering CD4 cell counts, with a statistically significant elevated risk related to a low CD4 /CD8 ratio. 1 Lymphocytopenia due to sequestration of lymphocytes at the tumor site is common in immunocompetent people with HL 3,4 and data from Clifford and colleagues 1 provide, for the first time, evidence for a decline in the number of circulating CD4 cells in the year preceding HL also in the setting of HIV infection. This observation makes timing of CD4 cell counts with respect to HL diagnosis a key element to help elucidate the still controversial relationship between degree of immune suppression and HL. From this viewpoint, it should be noted that, in the US study, CD4 cells were counted only once before HL and that only 27% of HL cases had a CD4 cell count available in the 12 months preceding HL onset. 2 This makes comparison of the findings of the 2 studies difficult.