2015 AP Biology free response 8

An individual has lost the ability to activate B cells and mount a humoral immune response.

Part A: Propose one direct consequence of the loss of B cell activity on the individual's humoral immune response to the initial exposure to a bacterial pathogen.

So, just as a reminder, what B cells are and what a humoral immune response is. The humoral immune response is one that involves antibodies, and B cells are the ones that will recognize an antigen—something that the body doesn't want in its body. In response to that, those antigens will produce, it'll proliferate, and it'll differentiate into plasma cells that produce antibodies, which are essentially these macromolecules that tag the antigens for cleanup. Then, it can differentiate into memory B cells so that next time when that same antigen shows up, it can mount a faster response.

So, part A: propose one direct consequence of the loss of B-cell activity on the individual's humoral immune response to the initial exposure to a bacterial pathogen. There won't be a humoral response. So, I could say no antibodies will be produced, so no humoral immune response. There will be no humoral immune response to the initial exposure. You're not going to have any tagging of these antigens; they're going to be cleaned up by other immune cells. None of that’s going to happen.

Part B: Propose one direct consequence of the loss of B-cell activity on the speed of the individual's humoral immune response to a second exposure to the bacterial pathogen.

Well, you have no memory B cells, no memory B cells and no antibodies, specific antibodies for the second exposure to the pathogen. So, no humoral response. Overall, the immune response will be slower. The whole point of B cells and the antibodies is that the second time it shows up, it gets tagged very quickly; it gets recognized very quickly. Then, the immune system can respond. Well, now you're not going to have that. You're not going to have this quick recognition of the antigen during the secondary exposure. So, you're not going to have a humoral response, and you could say the overall immune response will be slower. The immune response is going to be slower and less effective.

Part C: Describe one characteristic of the individual's immune response to the bacterial pathogen that is not affected by the loss of B cells.

Well, the B cells are all about the humoral immune response. It's about tagging things with antibodies and having the memory B cells around so that the next time you get the pathogen, during the second exposure, you have a quicker response. But it's not the only part of our immune system. Your immune system has still many facets to it.

One, you're still going to have the cell-mediated immune response. You still have cell-mediated immune response, and these are things like phagocytes that will go and engulf the pathogens. Phagocytes! You have T cells that can recognize the antigen and similarly try to go about destroying the antigen. So, you still have the cell-mediated immune response.

You also have things like the skin—things that just block pathogens from entering your body, and that's considered part of your immune system. You still have skin protection. You can go into more detail, but these are still the types of things that the body has, even if it lost its B cell capability, in order to prevent pathogens from entering, in the case of skin, and also still, once the pathogens get in, to recognize them and engulf them or destroy them in some way.