HN & CD3

In immunology, the CD3 (cluster of differentiation 3) T-cell co-receptor is a protein complex and is composed of four distinct chains. In mammals, the complex contains a CD3γ chain, a CD3δ chain, and two CD3ε chains. These chains associate with a molecule known as the T-cell receptor (TCR) and the ζ-chain to generate an activation signal in T lymphocytes. The TCR, ζ-chain, and CD3 molecules together comprise the TCR complex.

Hemagglutinin-neuraminidase refers to a single viral protein that has both hemagglutinin and neuraminidase activity. This is in contrast to the proteins found in influenza, where both functions exist but in two separate proteins.