Glycosylphosphatidyl Inositol-Linked Membrane-Protein Expression By Intestinal Intraepithelial Lymphocytes

Murine intestinal intraepithelial lymphocytes (iIEL) represent a heterogeneous population of cells which contains both TCR-alpha-beta+ and TCR-gamma-delta+ cells. In contrast to the TCR-alpha-beta+ cell population in peripheral lymphoid organs, the TCR-alpha-beta+ iIEL contain high numbers of Thy-1- cells. This negativity of iIEL for Thy-1, a glycosylphosphatidyl inositol (GPI)-linked membrane protein, is not the result of conformational changes of the Thy-1 molecule. The absence of Thy-1 on TCR-gamma-delta+ and a subset of TCR-alpha-beta+ iIEL is furthermore not caused by a general defect in the processing of GPI-linked proteins, since Thy-1- iIEL mainly express another GPI-linked protein, Qa-2. However, TCR-alpha-beta+ and TCR-gamma-delta+ iIEL are also virtually negative for two other members of this family of activation-associated GPI-linked proteins, Ly-6A and Ly-6C. This unusual pattern of GPI-linked protein expression on TCR+ iIEL may be related to differences in cellular activation and signal transduction pathways between TCR+ iIEL and regular peripheral T cells.