Research On The Mechanism Of Interaction Between TCR-CD3 Complex And MHC

In the human adaptive immune response system,the involvement of T cells in the immune response is crucial.In human body,the T cell receptor expressed on more than 90% of T cells is ??TCR,which can specifically recognize the major histocompatibility complex on the surface of antigen presenting cells and the antigen molecules presented by MHC,and carry out downstream signal transmission through its co-receptor CD3,thus initiating the specific immune response mediated by T cells.The specific recognition of the pMHC complex by the TCR-CD3 complex is a key link in the immune response of T cells.In recent decades,many scientists have conducted a great deal of research on the interaction mechanism and structural basis between the extracellular domains of TCR and pMHC.However,key questions about how the intact TCR-CD3 complex interacts with the pMHC complex and how TCR transmits signals to CD3 remain unanswered.In this study,mammalian expression system was used to express the purified TCR-CD3 complex and its co-receptor CD4,and escherichia coli expression system was used to express the purified pMHC complex inclusion body and obtain its active protein by dilution and renaturation.On the basis of obtaining the corresponding proteins,detected by molecular sieve chromatography,Octec RED96 e and TEM observation,and the TCR-CD3 complex was found to be directly bound to the pMHC complex,with an affinity of 70.7nmol/L.By joining CD4 molecules,crosslinking agent,and the introduction of point mutation to increase the stability and homogeneity of TCR-CD3-pMHC complex,results show that the methods of joining CD4 molecules as well as the introduction of point mutations make TCR-CD3 complex combined with pMHC complexes no significant effect,join the crosslinking agent can make the interaction between TCRCD3 and pMHC complex more closely,but in the end the homogeneity is still not high.In summary,this paper preliminarily explored the results of direct interaction between TCR-CD3 complex and pMHC complex,and studied the influence of the addition of CD4,cross-linking agent and the introduction of point mutation on the interaction between them,which provided the corresponding direction and basis for the subsequent structural biological studies on the interaction between TCR-CD3 complex and pMHC complex.