Question

when the immune system is scanning for problems, what is it mainly detecting?

- antigens on the surface of invading cells

- antibodies on the surface of cells that are "self"

-antibodies on the surface of invading cells

- antigens on the surface of cells that are " self"

Answer 1

Answer - antigens on the surface of invading cells.

Reason

- Antigens are actually protein substances which are capable of producing immune response which are found on the microbial surface and even in cells of our body

- those present in our body are referred as self antigens and those on microbial cell are referred as nonself antigens.

- As T cells of a healthy person remains inactive in presence of self antigens, it can't detect the self antigens. hence 4th statement is wrong.

- While the antigens on microbial pathogens can be detected by these T cells, hence can activate the immune response by presenting it to APC's, hence 1st statement is correct.

- Antibodies are those substances which are produced in response to invading antigens inorder to destroy them.

- the presence of antibodies can't induce any immune response, but it is a part of immune response, hence 2nd and 3rd statements are wrong.