Question

1. Describe the difference between Toll-like receptor specificity for PAMPs and antigen receptor specificity on lymphocytes. Why do you think these two systems exist, and what is the evolutionary relevance of the development of the recombination mediated process for generating T and B cell receptors?

Answer 1

Toll like receptors (TLRs) are membrane receptors present on body defence cells such as macrophages, dendritic cell, epithelial cells. These receptors recognize the PAMPs ( pathogen associated molecular pattern). TLRs identify the molecules produced by different microbes and binds to them.
The antigen receptor specificity of leucocytes are the specificity exhibited by B and T cell receptors to different kinds of antigen. B and T cell receptors are present on the surface of B and T cells and mostly identify the antigens based on their shapes and sizes.
The main difference between toll like receptors and antigen specific receptors is that TLR binds to molecules produced by antigens whereas antigen specific receptirs binds directly to the antigen itself.
Both TLR and antigen specific receptors helps in identifying antigen and activates the immune response to kill the foreign particles.
In recombination exons encoding the antigen binding portions of the receptor are assembled by chromosomal breakage and rejoined in developing lymphocytes. The exons encoding the antigen binding domains in lymphocytes are assembled from variables and gene segmentsare joined by DNA rearrangements. In recombination, a pair of segments is chosen and  introduces double-strand breaks adjacent to each segment, deletes the intervening DNA, and ligates the segments together. This helps in diversified antigen recognition.