Table I

Proteins regulated by cell activation

Unfractionated splenocytes were treated (16 h) or not with PMA/ionomycin (30 ng/ml each), cell-surface biotinylated, and PM proteins were recovered, resolved, and identified as described under “Experimental Procedures.” Proteins listed appeared up- or down-regulated (as indicated) as judged by differential silver staining in resting and activated cell extracts. Changes marked with an asterisk were selected for further study and subsequently confirmed by at least three independent Western or FACS experiments.

ProteinRegulation by PMA/ionomycin
IgM (membrane-bound form)Down*
IgD (membrane-bound form)Down*
Ig κ chainDown*
MHC class 2 α chain (I–Aq)Up*
MHC class 2 β chain (I–Aq)Up*
GITRUp*
Complement receptor-related proteinUp
CD21 (complement receptor 2)Up
CD22Up
CD26Up
CD69Up*
CD166 (ALCAM)Up
CD180Up