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5) Gamma-delta T cells are Weird. (Yes, that capitalization is intentional.) Although they undergo V(D)J recombination to produce their γδ chains, they have a limited repertoire of gene segments to use, and apparently only certain combinations are stable (for example Vγ9/Vδ2), further limiting what antigens they can see. Additionally, they do not require seeing MHC molecules with peptides to function, suggesting they do not always see protein-based antigens. Weirder yet, some γδ T cell subsets have the ability to phagocytose antigen and themselves function as antigen-presenting cells. Some scientists argue that these features suggest that γδ T cells are an evolutionary ‘left-over’, a bridging cell type between ancient innate immune cell types and the more recently developed adaptive cell types.  

Identify two other pieces of evidence from the text or literature and explain why they do or don’t support the idea that γδ T cells are “missing links” of the immune system.

(8 points, 4 per explanation)

Answer:

Gamma delta T cells (γδ T cells) are T cells with a specialized T-cell receptor (TCR) on their outer covering or surface. Comparisons between the δ and γ V, D and J gene portions within the primate species have shown a fascinating order of how these loci have evolved (Holtmeier & Kabelitz, 2005). The gene segments of the δ locus have not changed considerably in the primate ancestry from humans to marmosets; the gene directive, overall, is well-looked-after and most of the genes remain purposeful with few duplications or deletions.

Evolutionary perspectives of the Gamma delta T cells:

Gamma delta T cells are an enigma of the immune system. Their triggers are not really understood. An attempt to explain their role as the cells that bridge the gap between innate and adaptive immunity doesn’t really justify their niche in the immune system, rather it focuses on their complex behavior. Therefore, hypotheses can be derived from the inferences that are made as a bid to explain their fundamental behaviors, as follows:

First Hypothesis:

The gamma delta T cells are placed at the borderline between the innate immune response that is quick in its action against any agents whether it be pathogens or micro-organisms, coming from outside, and the adaptive immune response which is extremely specific in its action and uses the B and T cells to tailor an immune response for the body, against the incoming foreign agents. This is basically because of the uniqueness of the gamma delta t cells which bear TCRs, that are mostly invariant in nature. A good example in this regard would be the Natural Killer T cells that bear the CD1d-restricted sites (Holtmeier and Kabelitz, 2005). This hypothesis says that gamma delta t cells are indeed, the missing links between the two evolutionary types of immunity.

Second Hypothesis

The second hypothesis is a reinforcement of the fact that gamma delta T cells really are the missing links between the evolutionary steps of immunity. Some evidence has surfaced in the recent findings that confirm recent work has shown that Vγ9/Vδ2 T cells in human are also proficient enough to carry out complex processes such as the phagocytosis, a function previously found to occur only in innate myeloid lineage cells such as neutrophils, monocytes and dendritic cells (Holtmeier and Kabelitz, 2005). This makes the fact very credible that these cells are actually the link between the two types after all.

Answer 1

Gamma DeltaT cells are Tcells that have distinct Tcell receptor(TCR)on their surface.Most of Ycells are alpha-beta Tcells with TCR composed of two glycoprotein chains called a alpha and beta TCR chain.

In contrast,Gamma DeltaT cells have a TCR that is made up of one Gama Chain and one Delta chain.This group of Tcells is usually less common than alpha beta Tcells.Further more they are believed to have a prominent role in recognition of lipids antigens.They are of an invariant nature and may be triggered by alarm signals such as heat shock proteins(HSP).

We find that freshly isolated human peripheral blood Gamma DeltaT cells can phagocyte E.coli and 1 Micron synthetic beads via Ab opsonization and CD16 leading to Ag opsonization and presentation.In contrast,other lymphocytoses are not capable of such functions..

Most Gamma DeltaT cells recognise ligands which are fundamentally different from short peptides.

Gamma DeltaT cells in Autoimmunity: Autoimmune disease results from abnormal response of immune system. The role of Gamma DeltaT cells is to help B cells to produce autoantibodies, through proinflammatory cytokines.....

The above given answer is correct. And this can be added up.......