Priming to intracellular GFP facilitates antibody formation against the surface HOD antigen after HOD × GFP RBC exposure. (A) Experimental schematic of GFP priming, transfusion, and serum collection. (B) Anti-HOD IgG formation after HOD, HOD × GFP, or HOD + GFP RBC transfusion. (C) Anti-HOD IgG formation examined in PBS-treated, GFP-primed or B6-exposed recipients. (D-E) Anti-GFP IgM (D) or IgG (E) formation examined in PBS-treated, GFP-primed or B6-exposed recipients. Error bars represent mean ± SD. All panels show combined data from experiments reproduced at least 2 times. ∗∗∗ P ≤ .001 and ∗∗∗∗ P ≤ .0001. ns, not significant.