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How does the lack of MHC 1 on target cells influence the action of natural killer cells?
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The absence of MHC 1 acts as a trigger for natural killer cells to destroy the target cell, since healthy self-cells typically display MHC 1.
What primary and secondary signals are necessary for T helper cell activation?
The primary signal is the interaction of MHC 2 with TCR and CD4 proteins, and the secondary signal involves B7 and CD28 interaction.
What is the significance of T helper cell differentiation into Th1 and Th2 cells?
Th2 cells are essential for producing interleukins IL-4 and IL-5, which are critical for stimulating other immune responses like B cell proliferation and differentiation.
Why are natural killer cells considered part of innate, rather than adaptive, immunity?
Natural killer cells do not rely on antigen-specific receptors or previous exposure to antigens, acting instead on the absence of MHC 1 or stress markers.
How do cytotoxic T cells distinguish infected or cancerous cells in cell-mediated immunity?
Cytotoxic T cells recognize cells presenting foreign peptides on MHC 1 molecules.
In what manner do plasma cells contribute to an immune response?
Plasma cells produce antibodies specific to encountered antigens, helping neutralize or eliminate pathogens.
Explain the process through which natural killer (NK) cells eliminate target cells.
NK cells kill via the absence of MHC 1, presence of Ma molecules, or recognition of IgG, using mechanisms like perforins and granzymes similar to cytotoxic T cells.
Describe the role of IL-4 in B cell responses.
IL-4 stimulates the clonal expansion of B cells during an immune response.
How do B cell receptors achieve diversity in their antigen binding domains?
B cell receptors undergo recombination to vary their binding domains for different antigens.
In the context of adaptive immunity, what functions do antibodies perform?
Antibodies neutralize, precipitate, lyse, agglutinate, or opsonize antigens, helping connect adaptive and innate immunity.
How does humoral immunity differ from cell-mediated immunity?
Humoral immunity deals with external antigens through B cells and antibodies, while cell-mediated immunity addresses internal cell threats through cytotoxic T cells.
What is the importance of BCR endocytosis in B cell activation?
After antigen binding, BCR endocytosis allows for the processing and presentation of the antigen on MHC 2 molecules.
What role does IL-5 play in B cell maturation?
IL-5 induces B cell differentiation into plasma cells and memory B cells.
What is the function of interleukin 1 (IL-1) in T helper cell activation?
IL-1 is released for further signaling once T helper cells are activated.
What key structures within lymph nodes are primarily responsible for antigen presentation?
Germinal centers contain B cells, and macrophages and neutrophils carry antigens on MHC 2 molecules for presentation.
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