Surface Phenotype And Function

This in vitro clonal culture model may also be informative for longitudinal studies of age-related changes in TCC under chronic antigenic stress. Because of the constraints of the cloning procedure, young cells already have accomplished at least 22 or 23 PD, but at this stage, we still have a good representation of the starting repertoire (as discussed earlier). One of the simplest analytical techniques to study these cells over time is to use flow cytometry with monoclonal antibodies detecting molecules expressed on the cell surface. We have examined a large range of different surface markers and found relatively few that change with age (where aging is defined as increasing PD). The most common pattern of age-associated alterations involves a reduction of the level of expression of the costimulatory receptor CD28, and sometimes the putative costimulatory receptors CD134 and CD154 (Pawelec et al., 1997), whereas despite increased susceptibility to AICD, surface CD95 expression remains constant (Pawelec et al., 1996). The cells have a memory effector phenotype (CD45RA-negative, CCR7-negative, CD45RO+) as would be expected from chronically stimulated T cells. The level of the TCR also remains stable, suggesting that these cells retain the ability to recognize and respond to antigen. Major functional changes may follow from the decreased level of expression of costimulatory receptors, both CD28 and in all likelihood others yet to be investigated. The most dramatic changes are in the patterns of cytokines secreted, commonly resulting in decreased levels of IL 2 and increased levels of IL 10 (Pawelec et al., 1997). Because the expression of the TCR is maintained and antigen-specific signaling still occurs, it is likely that these differences are caused by differences in the delivery of costimuli to the T cells.

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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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