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The Immune System - Recognition in innate immunity. How?

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The Immune System - Recognition in innate immunity. How?

Postby hplc » Mon May 11, 2009 5:51 pm

Hello.

Hope you can help me with this question;

I've been reading about the aquired immune system, and I understand the recognition process that this immune response involves. But how does for example the macrophages (or another cell used in the innate immune system) recognize their targets? What decides whether the aquired immune system or the innate immune system eliminates a pathogen?

Also; an unrelated question; what is the structural difference between the IgG and IgE antibodies?

Thanks.
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Postby biohazard » Tue May 12, 2009 7:43 am

The innate immune system has many components (located on the cell surface or secreted into plasma, for example), but in general they target such pathogenic antigens/structures that are common to microbes but not present in the host body. This way the receptors that recognize these can be assembled straight from their respective genes (their specificity is inherited) - unlike receptors of the adaptive immune system, where each antigen-specific molecule (such as antibodies and T cell receptors) must be constructed individually from multiple genes by very complex mechanisms of recombination and mutation.

The components of the innate immunity (e.g. Toll-like receptor on macrophages, mannose-binding lectin in the plasma) have their specificity encoded on a genomic level, are expressed in similar form on the surface of every cell of a given type, trigger immediate response and are able to recognize a broad range of pathogens. They recognize e.g. specific sugars on the surface of the pathogen or lipopolysaccharides (LPSs). In general, these structures are called pathogen-associated molecular patterns (PAMPs) and are recognized by pattern recognition receptors (PRRs)

The adaptive immunity, on the other hand, is encoded by several genetic elements, require gene rearrangement, is extremely specific regarding its target molecule and relies on clonal expansion (each cell and its daughter cells of a given cell type have similar antigen recognizing receptor and specificity). It also involves more cell-cell interactions and use of co-receptors. Thus, the adaptive response is slower, but very specific, recognizing mostly protein or peptide motifs.

Thus, the type of immune response is largely determined by the type of the recognized molecule, as well as time; unless there is immunological memory (i.e. a re-infection or after vaccination), it takes several days from the adaptive immune response to kick in, whereas the innate one works immediately. If the infection persists, the adaptive response typically takes the main role in eradicating the pathogen.

IgE has a different heavy chain from IgG subtypes, and is capable of binding with high affinity to the surface of basophils and mast cells (Fce receptors). They also have different kind of disulphide bonding and N-linked carbohydrates when compared to IgGs.
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Postby ksherr00 » Thu Nov 19, 2009 5:01 am

In cell mediated immunity I was asked this question. Which of the following sets of cell tyes are involved in the process of cell mediated immunity?

1. CD8, APC, TH2
2. Cytotoxic T cells, Th1, APC
3. Mature Th1, MHC cells, APC

APC (antigen presenting cells)

I am so confused.
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