Question

Which of the following is true about T-cell receptors?

a. They are highly specific.
b. They are secreted after a T cell has been activated.
c. They are comprised of 4 chains.
d. They can be expressed as a soluble form.
e. All of the above are true.

Answer 1

The correct answer is a. T-cell receptors are highly specific. They consist of two chains (alpha and beta), are embedded in the T cell membrane, and cannot be secreted or expressed in a soluble form.

Step-by-step explanation:

The correct answer to the question about T-cell receptors (TCR) is option a. They are highly specific. TCRs are indeed highly specific for antigens presented with Major Histocompatibility Complex (MHC) molecules. TCRs are not secreted; they stay embedded in the T cell membrane.

T-cell receptors consist of only 2 chains, an alpha and a beta chain, so option c is incorrect. There is no known soluble form of the T-cell receptor, meaning option d is also incorrect. Therefore, option e, 'All of the above are true' is not the correct answer.

T-cell receptors are found on the surface of T cells and are crucial for the immune system's ability to recognize and respond to pathogens. The TCR comes from the same receptor family as immunoglobulins like IgD and IgM, but it has a simpler structure with just two chains.

TCRs are involved in the first step of pathogen epitope recognition during the activation process for both helper and cytotoxic T cells.

Helper T cells, which are CD4+, and cytotoxic T cells, which are CD8+, each have TCRs on their surface. It is important to note that the MHC II is expressed on antigen-presenting cells, not 'most body cells', and MHC I is found on all nucleated cells, not just immune cells. Therefore, the statement in option d from the second set of statements is false.