Question

All of the following are included in the central supramolecular activation complex (c-SMAC) except _____?

1) CD4 or CD8
2) ICAM-1
3) CD28
4) T-cell receptor
5) PKC-theta

Answer 1

ICAM-1 is the molecule that is not part of the central supramolecular activation complex (c-SMAC); instead, it is found in the peripheral supramolecular activation complex (p-SMAC).

Step-by-step explanation:

All of the following are included in the central supramolecular activation complex (c-SMAC) except ICAM-1. The c-SMAC is a part of the immunological synapse, which is formed during the activation of T cells. The constituents of the c-SMAC include:

• CD4 or CD8 - co-receptors that define the specificity of the T cell (helper T cells have CD4, while cytotoxic T cells have CD8).
• CD28 - a costimulatory molecule necessary for T cell activation.
• T-cell receptor (TCR) - the receptor that recognizes and binds to antigens presented by MHC molecules on antigen presenting cells.
• PKC-theta - a kinase that plays a critical role in the signal transduction pathways leading to T cell activation.

ICAM-1 is actually found in the peripheral supramolecular activation complex (p-SMAC), which surrounds the c-SMAC and is involved in strengthening the interaction between the T cell and the antigen-presenting cell.