IMMUNOLOGY

Detailed explanation-1: -In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells.

Detailed explanation-2: -CD4 cells are a type of white blood cell. They’re also called CD4 T lymphocytes or “helper T cells.” That’s because they help fight infection by triggering your immune system to destroy viruses, bacteria, and other germs that may make you sick.

Detailed explanation-3: -The T-cell receptor (TCR)–CD3 complex is composed of a diverse TCR heterodimer noncovalently associated with the invariant CD3 dimers CD3, CD3, and CD3. The TCR mediates recognition of antigenic peptides bound to MHC molecules (pMHC), whereas the CD3 molecules transduce activation signals to the T cell.