Introduction to Lymphocyte Recirculation – Lymphocyte Recirculation and Homing

00:01 Let us explore lymphocyte recirculation and homing.

00:05 So why do lymphocytes recirculate around the body? Well, lymphocytes collectively have millions of different antigen specific receptors - the B-cell receptor on the surface of the B-lymphocyte, the T-cell receptor on the surface of the T-lymphocyte.

00:22 And therefore, for each antigen specificity, there are only initially a small number of T-cells and B-cells.

00:34 Also the adaptive response requires dendritic cells in order to activate naïve T-cells.

00:40 It needs helper T-cells.

00:42 And it needs the cognate B-cells, that is B-cells with the same antigen specificity as the T-cells to interact with each other.

00:52 Lymphocytes therefore need to seek out their antigen, they need to travel around the body to find antigen.

01:00 So they recirculate through the blood, the lymph nodes, the efferent lymphatics, and then eventually back to the blood circulation.

01:09 Meanwhile dendritic cells can pick up antigen in the tissues and migrate via the afferent lymphatics to the local draining lymph nodes.