Immune system

[chiddler]

Which statement will be challenged if it is discovered that that macrophages are present along with lymphocytes taken from strain B animals after they have been exposed to strain A antigens?

A. Transplant rejection is the result of an inflammatory reaction.

B. Second tissue rejection is a demonstration of immunologic memory.

C. Transplant rejection is caused by specific immune defenses.

D. Second tissue rejection occurs faster than first rejection.

Answer: C.




Macrophages are nonspecific. Lymphocytes are specific. Therefore, if macrophages are present, then there is a non-specific reaction occuring.

C is clearly the best answer.

My question is: What about A? Inflammation is due to T-cells which are specific. If there are more than just T-cells, then it must be more than an inflammatory reaction.

I realize that C is the best answer. But A is also a possible, but not as good answer, right?

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[MedPR]

Which statement will be challenged if it is discovered that that macrophages are present along with lymphocytes taken from strain B animals after they have been exposed to strain A antigens?

A. Transplant rejection is the result of an inflammatory reaction.

B. Second tissue rejection is a demonstration of immunologic memory.

C. Transplant rejection is caused by specific immune defenses.

D. Second tissue rejection occurs faster than first rejection.

Answer: C.




Macrophages are nonspecific. Lymphocytes are specific. Therefore, if macrophages are present, then there is a non-specific reaction occuring.

C is clearly the best answer.

My question is: What about A? Inflammation is due to T-cells which are specific. If there are more than just T-cells, then it must be more than an inflammatory reaction.

I realize that C is the best answer. But A is also a possible, but not as good answer, right?

There's a lot more to inflammation than T cells. All sorts of cells show up to the site; macrophages being one of those cells. Keep in mind that inflammation is considered an innate (non-specific) response.

 

[chiddler]

Oh I didn't realize inflammation was non-specific.

 

[Morsetlis]

Inflammation can be thought of was due to IL-1, TNFa, IFNy, CRP, and Histamine.

Th1 responses by T cell polarize toward TNFa, IFNy, and cytotoxic response which then leads to Th1 T-cells spitting cytokines and coordinating CD8+ and NK cells to destroy the intruder (usually a virus)
.
Th2 responses by T cell polarize toward CRP, Histamine, and antibody-mediated response, which then leads to vascular permeability, complements, opsonization, and phagocytosis (allergies, fungal, extracellular bacterial).

Macrophages phagocytosing due to PRP (Pattern recognition receptors) is non-specific, but phagocytosis due to opsonization (IgG, C3b, and CRP) can be specific (IgG) or nonspecific.

As well, macrophages synthesize cytokines, such as IL-1,6,12,15,18, and TNFa.

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The question is asking: If macrophages and lymphocytes are both present in an immune reaction involving different species. Which of these statements do NOT describe an immune reaction that involves both macrophages, and lymphocytes (meaning memory cells have formed, for specificity)?

A is true. Both macrophages and lymphocytes cause inflammation.

B is true. Immunologic memory T and B cells mediate secondary immune response.

C is true only in hyperacute rejection (specific preformed antibodies, without previous exposure). In acute and chronic rejection, the T cells recognize histo-incompatibility via HLA differences, and cytotoxicity occurs via lymphocytes. As well, DAF and HRF (complement regulatory proteins) are species-specific and complements can start to attack the cells, leading to opsonization and possibly phagocytosis.

D is true, because of formation of memory lymphocytes.

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I think the take-away message is that transplants are naturally, innately incompatible due to NON-specific immune reactions. Macrophages are USUALLY nonspecific, and lymphocytes are USUALLY specific, especially after formation of memory cells (except for CD8+ and NK cells, which are nonspecific but recognize your own MHC-I, and not foreign MHC-I).