α-Defensins released into stimulated CD8+ T-Cell supernatants are likely derived from residual granulocytes within the irradiated allogeneic peripheral blood mononuclear cells used as feeders

We recently demonstrated the ability of human alpha-defensins to inhibit HIV-1 replication in vitro and demonstrated that alpha-defensins account for the great majority of beta-chemokine independent antiretroviral activity in stimulated CD8+ T-cell culture supernatants. In a follow-up study aimed at defining specific subpopulations of CD8+ T-cells that produce alpha-defensins, we have found that in the absence of irradiated allogeneic peripheral blood mononuclear cells (PBMC), Stimulated CD8+ T-cell supernatants do not contain a-defensins. In our present work, we define residual granulocytes within PBMC fractions as the likely source. In addition, we describe in vitro conditions that promote the internalization of alpha-defensins by cells not natively producing these proteins, thus confounding our ability to define true alpha-defensin producer cells. In light of these findings, alpha-defensins released into stimulated CD8+ T-cell supernatants are unlikely to be derived from the CD8+ T-cells themselves. Moreover, our data imply that under some experimental conditions, a soluble noncytolytic anti-HIV-1 factor other than beta-chemokines is either not produced by CD8+ T-cells or is present in too small quantity to be effective.