CD19 and neoplasm: Antigen-specific 2C T cells, which recognize the synthetic SIYRYYGL peptide (SIY) in the context of the murine MHC H-2Kb, were recruited using either a peptide loaded MHC-Ig complex (SIYKb-Ig) or an anti-clonotypic antibody (1B2); tumor cells were recruited with an anti-human-CD19 (Figure 1A).