CD20 & CD28

This gene encodes a member of the membrane-spanning 4A gene family. Members of this nascent protein family are characterized by common structural features and similar intron/exon splice boundaries and display unique expression patterns among hematopoietic cells and nonlymphoid tissues. This gene encodes a B-lymphocyte surface molecule which plays a role in the development and differentiation of B-cells into plasma cells. This family member is localized to 11q12, among a cluster of family members. Alternative splicing of this gene results in two transcript variants which encode the same protein.

CD28 is a co-stimulatory receptor found on T cells that plays a key role in T-cell activation and survival. It is a transmembrane protein expressed on naïve and activated T cells, binding to B7-1 (CD80) and B7-2 (CD86) on antigen-presenting cells (APCs). This interaction provides the necessary secondary signal for full T-cell activation, alongside T-cell receptor (TCR) engagement with antigen-presenting major histocompatibility complex (MHC). CD28 signaling promotes cytokine production, T-cell proliferation, and survival. In the absence of CD28 signaling, T cells may become anergic (non-responsive). Because of its role in immune regulation, CD28 is a target for therapeutic interventions in autoimmune diseases, transplantation, and cancer immunotherapy.