Question

What happens to a naive T-cell when it encounters a cell that: (1) expresses an antigen for which the T-cell receptor (TCR) has high affinity and to which the TCR strongly binds, (2) does not express MHC molecules?

	A.	It differentiates into a cytotoxic T-cell and produces toxic molecules that kill the encountered cell.
	B.	It is negatively selected and induced to undergo apoptosis or to become inactivated.
	C.	It differentiates into one of the several subtypes of T-helper cells according to the surrounding cytokine environment.
	D.	It undergoes positive clonal selection and proliferates.

Answer 1

A T-cell when encounters a cell that:

(1) Expresses an antigen for which the T-cell receptor (TCR) has high affinity and to which the TCR strongly binds,

It differentiates into one of the several subtypes of T-helper cells according to the surrounding cytokine environment.

(Since it differentiates to TH1 or TH2 which further differentiate to either T helper or Memory T cells or Cytotoxic T -cells depending on the cytokine environment).

(2) does not express MHC molecules,

it is negatively selected and induced to undergo apoptosis or to become inactivated.  

(T cells that do not bind to MHC either die by apoptosis (in non-lymphoid organs) or they get inactivated enter the, thoracic ducts, and get back into the blood circulation).