Question

One type of bare lymphocyte syndrome is caused by a genetic defect in MHC class II transactivator (CIITA), which results in the inability to synthesize MHC class II and display it on the cell surface. The consequence of this would be that _______________.

1) The immune system would not be able to recognize and respond to foreign antigens
2) The immune system would not be able to produce antibodies
3) The immune system would not be able to activate T cells
4) The immune system would not be able to recognize self-antigens

Answer 1

The consequence of a defect in CIITA, preventing synthesis and display of MHC class II, is that the immune system would not be able to activate T cells. This directly impairs the immune response, including antibody production by B cells.

Step-by-step explanation:

If a genetic defect in MHC class II transactivator (CIITA) causes an inability to synthesize and display MHC class II on the cell surface, the consequence would be that the immune system would not be able to activate T cells. MHC class II molecules are essential for the proper function of the immune system because they present antigens to CD4+ T cells, which are a type of helper T cells. Without MHC class II, these helper T cells cannot be activated, which impairs the immune response, including the production of antibodies by B cells.

While recognizing foreign antigens and producing antibodies are important functions of the immune system, they are dependent on the prior activation of T cells, which in this case is hindered without MHC class II molecules. On the other hand, recognizing self-antigens is more relevant to MHC class I molecules; therefore, the inability to activate T cells is the direct consequence of the scenario described.