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