Flow cytometry

Hi. Can someone please check my answers to the following multi-part question, and explain the questions I couldn't answer or that I got wrong?

This is an 11-part question (!), but I think it looks worse than it is. It's 60% of a 1-hour test, so I don't think it should take more than an hour to go through, at most.

For the question, please go to the following website: http://tutor.lscf.ucsb.edu/instdev/sears/immunology/

Click on prior examinations; password: gauchos

Go to winter 2003 midterm, question #2. (My professor gave out previous years' exam questions, but not answers.)

One thing I'm particularly concerned about in my answers is that I didn't take into account any differences between spleen lymphocytes and thymus lymphocytes, because I wasn't sure what those differences might be.

Here are my answers:

A. T cytotoxic cells -- because these are CD8+,CD4- lymphocytes.

B. T helper cells -- because these are CD4+,CD8- lymphocytes.

C. These are CD4-,CD8- (double negative) lymphocytes, so they could be either B cells or NK cells, both of which are lymphocytes that lack CD4 and CD8 markers.

D. These are TCR(alpha,beta)+, CD8- lymphocytes, so they are probably T helper cells. They could also be NK cells (which would have an alpha beta T cell receptor, and would lack a CD8 marker.)

E. TCR(alpha, beta)+, CD8+ lymphocytes = T cytotoxic cells.

F. TCR(alpha,beta)-, CD8- lymphocytes = B cells. The only lymphocytes that lack T cell receptors are B lymphocytes.

G. I'm not sure about this one. Could they be T cytoxic cells that have TCR(gamma, delta) instead of TCR(alpha, beta)?

H. I'm *guessing* that it's the lower left quadrant based on the fact that those cells are CD4-,CD8- and hence can't function as T helper cells or T cytotoxic cells. But couldn't those cells be B cells or NK cells, rather than functionally immature cells?

I. I have no idea. Please help!

J. I would *guess* that the answer is T helper cells since there seem to be relatively small changes in their populations from the normal mice to the knockout mice. Or is a more accurate answer "all CD8- cells, including T helper cells, B cells, and NK cells"?

K. I have no idea. Please help.

Thank you!!