DUODENAL INTRAEPITHELIAL-GAMMA-DELTA T-CELLS AND SOLUBLE CD8, NEOPTERIN, AND BETA-2-MICROGLOBULIN IN SERUM OF IGA-DEFICIENT SUBJECTS WITH OR WITHOUT IGG SUBCLASS DEFICIENCY

Expression of the gamma/delta T cell receptor (TCR) on CD3+ intraepith elial lymphocytes (IELs) was studied by two-colour immunofluorescence in duodenal tissue sections from healthy (n = 6) or infection-prone (n = 7) subjects with selective IgA deficiency (IgAD), and subjects (n = 4) with combined IgAD and IgG subclass deficiency. TCRgamma/delta+ IE L proportions in selective IgAD subjects (median 6.3%, range 1.0-41%) and in those with combined deficiency (median 4.5%, range 1.2-33%) wer e well within the range (0.3-38%) for histologically normal controls ( n=11), but the healthy IgAD subgroup tended to show raised TCRgamma/de lta+ IEL proportions (median 13-6%) compared with the other two subgro ups. Also the number of TCRgamma/delta+ IELs per intestinal length uni t was relatively high (median 13.9/mm) in the healthy IgAD subjects, a nd significantly raised (P < 0.03) compared with controls (median 3.2/ mm). Paired staining revealed that most TCRgamma/delta+ IELs in both s elective IgAD (98%) and combined deficiency (99%) were CD8-, and a lar ge fraction (median 84% and 63%, respectively) expressed the Vdelta1/J delta1-encoded epitope. The total number of CD3+ IELs (mostly CD8+) wa s similar to controls. IgAD subjects, and especially the healthy subgr oup, had significantly increased serum concentrations of soluble CD8 ( P<0.0002), neopterin (P<0.005), and beta2-microglobulin (P < 0.007), w hich was similar to our previous observations in common variable immun odeficiency, and probably reflected stimulation of cell-mediated immun ity. In addition, the increased TCRgamma/delta+ IELs might reflect a c omponent of compensatory surface protection in the healthy IgAD subgro up.