Classify the events as possible precursors for a professional antigen presenting cell (pAPC) activating Signal 1, Signal 2, or Signal 3 in an interaction with a naïve CD4+ T cell. Not all of the events will be used. Signal 1 MHC restriction endogenous pathway of antigen presentation V(D)J recombination lineage commitment Signal 2 Signal 3 exogenous pathway of antigen presentation PRR signaling in pAPC activates CD80 expression PRR signaling in pAPC activates IL-2 expression Answer Bank IL-2α chain gene expression

Classify the events as possible precursors for a professional antigen presenting cell (pAPC) activating Signal 1, Signal 2, or Signal 3 in an interaction with a naïve CD4+ T cell. Not all of the events will be used. Signal 1 MHC restriction endogenous pathway of antigen presentation V(D)J recombination lineage commitment Signal 2 Signal 3 exogenous pathway of antigen presentation PRR signaling in pAPC activates CD80 expression PRR signaling in pAPC activates IL-2 expression Answer Bank IL-2α chain gene expression