for you immunologists

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wishuponastar

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what is the difference between humoral and cell mediated immunity? I understand what is out of the Kaplan book and various other study books with regards to the different antibodies and the the T lymphocytes and B lymphocytes and the lymphocyte precursors with primary responses and memory responses...but in terms of humoral vs. cell mediated, what do those even mean? thanks. Also, could someone please explain the histamine response with allergies? Like, why your nose runs...that whole thing, because it just has not sunk in yet...Thanks.
 

killinsound

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in really simple wording:

humoral (b cell mediated) is in a response to antigens.

cell mediated (t cell) is in response to infected host cells.

they are both linked to each other.
 

Mark84

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granular lymphocytes are generally the cause of allergic reactions, basically your body is recognizing something (pet dandruff) as a foreign antigen that could be dangerous to your body. Although this isn't the case your body will respond by attacking the allergen which causes runny nose, itchy eyes ect. in the process. I wouldn't expect you would have to go much deeper into the exact mechanisms of immune response.
 

booji

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The classification for humoral immunity actually comes from the fact that plasma contains antibodies against antigen. It was noted using rabbit serum that serum transfusion from an infected rabbit (2 weeks post infection) to a non-infected rabbit. When the non-infected rabbit was then treated with the antigen, it showed a "secondary" immune response indicating that antibodies were transfered along with the serum transfusion. Hence, this is referred to as the humoral immune response.

Cell mediated immunity as somone already mentioned is exactly like what the name describes. Cells actually have to mediate the immune response. An excellent example is TCMC (T-Cell Mediated Cytotoxicity).

Good Luck
 

CD4helpCD8

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Just add a couple of points here (finally, seven years of PhD training in immunology paid off :D ):

(1) Both humoral and cell-mediated immune responses are part of the adaptive immunity, and the effrector cell populations are lymphocytes (both B and T cells). In comparison to the innate immune system (which include neutrophils, macrophages, etc), the adaptive immune system is characterized by (a) high specificity; (b) memory.

(2) "Granular lymphocytes" is not a technically correct term (sorry Mark84 :p ). Lymphocytes (T and B cells) and granulocytes (neutrophils, basophils, eosinophils, etc.) are derived from two different lineage precursors (common lymphoid progenitor and common myeloid progenitor, respectively). Some T cells (e.g. CD8+ T cells) do have granules, but that has nothing to do with IgE-mediated allergic reactions.

(3) Though the primary focus of immune responses is to defend host from infections, keep in mind that NOT all immune responses are against microbes/viruses/parasites. One good example is tumor immunity (immune responses against tumor antigens), which can be essentially an autoimmune response (response against self antigens, such as PSA in prostate cancer).

(4) About allergies: When individuals are exposed to allergens (antigens that trigger allergies), some B cells in their bodies make IgE (one of the five antibody isotypes) in responding to these allergens. These IgE will bind to and crosslink the Fc receptors on mast cells and basophils, and this crosslinking will trigger mast cells and basophils to release their granules, which contain histamine. Histamine will then cause vasodilation and increase blood vessel permeability (running nose/nasal congestion) and smooth muscle contraction (as seen in asthma).

I don't think you need advanced knowledge in immunology to deal with MCAT though :) . Good luck!
 

metastasis

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I have a question.

Is negative selection mediated by the thymic cortical epithelial cells or the bone marrow derived cells (such as APCs). I know this isn't on the MCAT, but I was just wondering what other people think. When I took immunology some time ago, I was taught that positive is mediated by the thymic cortical epithelial cells, while negative is by bone marrow derived ells. However, one of my friends taking it right now was telling that both are mediated by the thymic cortical epithelial cells.

THanks.
 

dipak_ramkumar

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I believe positive selection occurs by the cortical epithelial cells of the thymus (for T-cells) and I believe negative selection occurs through the nurse cells. I might have double check though.
 
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