In addition, there may be subsets of CD4 memory cells that are not biased toward any lineage,

and so display the highest degree of lineage potential following reactivation with antigen. In the case of such non-committed cells, the prediction would be that lineage-associated transcription factor and/or effector genes (i.e Tbx21/Tbet, Gata3, Rorg, Bcl6, IFNg, IL4, etc.) have not yet acquired epigenetic Selleck 3-deazaneplanocin A modifications consistent with expression of these genes that would skew their response toward any particular lineage. In depth gene expression and epigenetic analysis of memory subsets will be useful in determining whether ‘Th uncommitted’ memory CD4 T cells contribute significantly to the pool of memory T cells. Further, analysis of on-off-on gene regulation for genes such as CD62L, CCR7 and Bcl2 in memory cells will be useful for understanding factors that govern homing and survival during homeostasis Selleck Cetuximab in the absence of their antigen, and possibly be predictive of the fate of memory cells following re-encounter with antigen. It is essential to understand how antigen-specific CD4 memory T cells behave in response to repeated exposure to pathogen, or throughout the course of vaccination, where priming and repeated boosting to antigen, results in reactivation of memory cells. Determining whether memory CD4 T cells ‘remember’ and

efficiently recall lineage-specific gene expression programmes that were acquired during their progenitors at the effector stage will provide an important framework for predicting the capacity of memory CD4 T-cell subsets to provide cellular immune responses and provide help for humoral immune responses

upon boosting or challenge with pathogen. A shared feature of CD4 and CD8 T-cell memory differentiation is ioxilan that the strength and duration of TCR signalling determines the function and phenotype of the cells. At the extreme end of the TCR strength/duration of the signal spectrum are cells differentiated during chronic viral infections. Therefore, additional insights into the mechanism for differentiation of functional memory T cells may be gained from interrogating the mechanism for development of non-functional memory cells during conditions of antigen persistence. Failure to control viral infection results in a diminished ability of antigen-specific CD8 T cells to rapidly up-regulate cytokine expression and to kill antigen-presenting cells, often regarded as T-cell exhaustion.[52, 53] It is now well accepted that these functionally impaired exhausted T cells can be rejuvenated through manipulation of their inhibitory receptor signalling, and therapeutic strategies that target these inhibitory mechanisms play an important role in clearance of chronic viral infections such as HIV or hepatitis C virus, as well as control of several types of cancer.