PHENOTYPIC, FUNCTIONAL AND MOLECULAR ANALYSIS OF CD3(-) EXPANSIONS INDICATES A RELATIONSHIP TO 2 DIFFERENT CD3(-) NORMAL COUNTERPARTS

In this study we have analysed the CD3 and TCR transcript expression i n CD3(-) granular lymphocyte (LGL) expansions. These LGL populations s how a heterogenous pattern of expression for CD2, CD8, CD16, CD56 and CD57 antigens. LGL1 is CD2(+)CD8(-)CD16(+)CD56(+)CD57(+), while LGL2 i s CD2(-)CD8(+)CD16(-)CD56(-)CD57(-); LGL3 is similar to LGL1, except f or CD8 antigen expression. Functional analysis has revealed a differen t behaviour of these LGL expansions in a cytotoxicity assay against th e NK-sensitive K562 cell line. LGL1 and 3 display a significant NK-lik e activity, while LGL2 is inefficient against K562 target cells. TCR a nd CD3 transcript characterization of LGL expansions 1 and 3 showed th at they expressed multiple TCR delta transcripts, a nonfunctional TCR beta transcript, CD3-zeta and -epsilon mRNA, but they lacked CD3 delta transcript and they lacked or expressed at very low levels of CD3 gam ma transcript. On the other hand, LGL2 expressed TCR delta, CDS-gamma, -epsilon and -zeta transcripts, while it lacked CD3 delta mRNA. On th e basis of these data, LGL1 and 3 seem to be closely related to periph eral blood mature natural killer (NK) cells, whereas LGL2 displays a p attern of TCR and CD3 expression similar to that found in CD1(-)2(-)3( -)4(-)8(-)16(-)thymocytes.