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CD7 may be regarded as a pan T-cell marker that is useful for identifying T cells from very early stages of maturation. However, its value is limited by a high frequency of aberrant expression by other lineages that means caution is required in its interpretation Variation of expression of CD7 by mature t cells can have diagnostic value in particular there is frequentl loss of CD7 expression in many cases of Sezary syndrome

details CD7 is a transmembrane protein that supports T cell interactions with B cells during lymphoid development. Expression is acquired during thymic development of T cells appearing before other t-lineage markers, and expression is retained by mature t cells. Very consistent expression by T-all from an early pro-t stage of maturation. However, expression frequently in aml and may occur in b-all

• loss of CD7 expression occurs in mycosis fungoides and su8c3a9zary syndrome and can contribute to diagnosis
• quantitative expression of CD7 is seen with high levels of expression in t-all and t-pll, but lower in atll and lgl disorders