The restrictive role of sialic acid in antigen presentation to a subset of human peripheral cd4+ t lymphocytes that requires antigen‐presenting dendritic cells

Abstract

Dendritic cells from human epidermis, i.e., Langerhans cells (LC), are more potent antigen‐presenting cells (APC) than APC from peripheral blood in proliferative in vitro responses of helper T lymphocytes to various soluble antigens. Analysis of antigen recognition by CD4⁺ T lymphocyte clones indicated that this increased potency of LC as APC results from a preferential requirement for LC of part of the T cell population. These T cells show a long‐lasting restoration of antigen responsiveness to peripheral blood APC after antigen‐specific restimulation in vitro, indicating that restrictive antigen recognition concerns T cells that are not fully differentiated. A similar restrictive antigen recognition was observed by treatment of the T cells or the APC with neuraminidase. This restoration of responsiveness is associated with the occurrence of nonspecific cell clustering between T cells and APC. These results suggest that the selective requirement for APC is regulated by the function of adhesion molecules that are functionally blocked by sialic acid groups on immature peripheral T cells but that are readily available on peripheral T cells at a later stage of differentiation.