Identification of antigen-specific T cells has yielded valuable information on pathologic process and the disease state. Assays for quantification of inflammatory cytokines or lytic-granule molecules have been generally used to evaluate antigen specific T cell response, however their applicability have been hampered due to the limited source of autologous antigen-presenting target cells (APC).

K562, a leukemic cell line deficient of human leukocyte antigen (HLA), was transfected with a gene encoding HLA-A^*02 (K562/A^*02) and its function as stimulator cells in inducing activation of HLA-matched T cells was evaluated by IFN-γ enzyme linked immunospot (ELISPOT) assay.

The stable transfectant K562/A^*02 pulsed with HLA-A^*02 restricted peptide could specifically induce IFN-γ secretion by CD8+ T cells compared to no detectable secretion by CD4+ T cells. However, CD56+ NK cells secreted IFN-γ in both K562/A^*02 with peptide and without peptide. The number of IFN-γ secreted CD8+ T cells was increased according to the ratio of T cells to K562 and peptide concentration. Formalin-fixed K562/A^*02 showed similar antigen presenting function to live K562/A^*02. Moreover, K562/A^*02 could present antigenic-peptide to not only A^*0201 restricted CD8+ T cells but also CD8+ T cells from A^*0206 donor.

These results suggest that K562/A^*02 could be generally used as target having specificity and negligible background for measuring CD8+ T cell responses and selective use of K562 with responsder matched HLA molecules on its surface as APC may circumvent the limitation of providing HLA-matched autologous target cells.