Immunology Question---need help

[applicant2002]

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Greetings.

I have a question. When CD4 cells are activated, some secrete IL-2 and gamma interferon to activate CD8 cytotoxic cells.

CD4 cells also stimulate proliferation of CD4 cells. This is monoclonal proliferation because of the interaction of the IL-2 receptor and IL-2.

(The Antigen presenting cell expresses B7 which binds to CD28 on the CD4 cell, and this binding stimulates CD40 expression on the CD4 cell, which binds to the CD 40 receptor on the APC, which causes secretion of IL-1 from the APC, which stimulates IL-2 secretion from the CD-4 cell, which stimulates IL-2 Receptor expression on those CD-4 cells that have all these binding interactions. So basically, only those cells with the IL-2 receptor will proliferate)

However, is there a similar mechanism for CD8 activation via helper cells?

When CD8 cells are activated, is it just a general activation when then gets more specific because of the specific antigen in the body, or is it a specific monoclonal activation that activates only CD8 cells that are specific for the antigen that stimulated the CD4 cell in the first place?

Please don?t tell me to do my own homework? That?s what I?m doing and I?m stuck?I?m not trying to be lazy.


Have a wonderful day.

 

[ckent]

Originally posted by applicant2002


However, is there a similar mechanism for CD8 activation via helper cells?

When CD8 cells are activated, is it just a general activation when then gets more specific because of the specific antigen in the body, or is it a specific monoclonal activation that activates only CD8 cells that are specific for the antigen that stimulated the CD4 cell in the first place?

Please don?t tell me to do my own homework? That?s what I?m doing and I?m stuck?I?m not trying to be lazy.


Have a wonderful day.

I've always thought that the key to understanding immunology was to not think about it too much. Because a lot of it is still in the theoretical stage, and quite frankly, won't make any sense if you think about it too much, or if you are to experiment on it with in vivo models. The current research suggests that CD8 cells are activated by MHC I + antigen (could be viral particles, or mutated or foreign proteins) interaction, and CD28-B7 co-stimulation to start expressing IL-2 receptors. Once these IL-2 receptors are being expressed, they respond to the IL-2 being secreted by the the activated CD-8 cells and the activated CD-4 cells (that just "happen" to be in close proximity, this is where you need your imagination, to think that a CD-4 cell that is recognizing a completely different antigen being presented by a completely different cell happens to be close by to an activated CD-8 cell in the same area). Remember that non-memory CD-8 cells can't activated without CD-4 cells. Also keep in mind that "memory" cells are a myth, everybody believes that they exist, but no one's actually been able to find where they all hang out. Therefore, only the CD-8 cells that have been activated ( or are specific) proliferate, so you don't have a general proliferation of non-specific CD-8 cells, you only should have a proliferation of antigen specific CD-8 cells. I don't remember the specifics anymore, I actually had to look up which molecules were responsible for the co-stimulation since it's been so long since I studied this stuff. It's fascinating stuff, but it's such a new field, and so much is based on "conceptualization" versus actual observation, that I think that in ~10 yrs, they will be completely re-writing the text books again.

 

[Dr JPH]

Look it up in Janeway.

 

[applicant2002]

thanks a lot for that explanation ckent. it kinda put things in perspective for me.

and thanks for the reference jp--i was just informed by a classmate that that book is free on ncbi so I'll take a look at it online.