In: Biology
Discuss the complexity of the TCR and two of its accessory partner receptors [PD-1, ox40] which appear to regulate the response mechanism within the cell. How do the partners impact the story?
The PD-1 known as programmed cell death-1 receptor is usually expressed on the surface of the activated T cells. The ligands for PD- 1 known as PD-L1 and PD-L2 are expressed on the surface of cells such as the dendritic cells or the macrophages. PD-1 and PD-L1/PD-L2 act as immune checkpoint proteins and co-inhibitory factors that fucntion to out a limit to the development of the T-cell response.PD-L1 that is expressed on the tumor cells binds to the PD-1 receptors expressed on the surface of the activated T cells that leads to the inhibition of the cytotoxic T-cells.These deactivated T cells then are kept inhibited in the tumor microenvironment.The PD-1/PD-L1 interaction also ensures the fact that the that the activation of immune systen is only done when required so that the possibility of chronic autoimmune inflammation is minimised.
OX40 (CD134) along with its binding partner i.e OX40L (CD252), belong to the tumor necrosis factor receptor superfamily and these are are expressed on the surface of activated CD4(+) and CD8(+) T cells.Costimulatory signals that generate from OX40 to the T-cell results in the promotion of its division and survival. OX40 in addition to this,suppresses the differentiation and activity of the regulatory T-cells along with other activities such as regulation of cytokine production from T cells, antigen-presenting cells, natural killer cells, and natural killer T cells, and also modulates the signalling from cytokine receptor.T