CD40, a member of the TNF receptor superfamily, is expressed on both immune and non-immune cells. Its interaction with CD40L (predominantly expressed on activated CD4+ T cells) is crucial in promoting germinal center formation and class-switched antibody production. This interaction also participates in CD4+ T cell priming by dendritic cells, CD4+ T cell help to B cells, and classical macrophage activation, and is involved in many immune-related pathways [1,2].

CD40-CD40L interaction has been implicated in various disease conditions. In autoimmune diseases, it may contribute to pathogenesis on both hematopoietic and non-hematopoietic cells [1]. In the context of type 2 immunity, while its role in helminth infection remains incompletely understood, CD40 and CD154 (CD40L) are necessary for most Th2 responses [2]. In atherosclerosis, the CD40-CD40L system is a potential immune-therapy target, though long-term direct suppression may lead to immunosuppression [3]. Also, the CD40-CD154 interaction is involved in the pathogenesis of numerous inflammatory and autoimmune diseases, and soluble CD40 receptor may serve as a biomarker for chronic inflammatory diseases [4].

In conclusion, CD40 plays essential roles in immune-related biological processes, especially in antibody production and T-cell-mediated immune responses. Research using models (implied by the studies on its role in various diseases) has revealed its significance in autoimmune diseases, type 2 immunity, atherosclerosis, and chronic inflammatory diseases. Understanding CD40's functions provides potential therapeutic targets for these diseases.