Monoclonal antibodies to influenza matrix protein: detection of low levels of matrix protein on abortively infected cells.

We have quantified the appearance of matrix (M-) protein on P815 mastocytoma cells infected with type A influenza virus using a monoclonal antibody specific for M-protein. In contrast to previously reported values, only low amounts (about 10(3) molecules/cell) of M-protein appear on the cell surface up to 16 h p.i. Since P815 cells are excellent targets for cross-reactive T-cell lysis 3 to 5 h after virus infection, when only about 10(2) M-protein sites are found on each cell surface. It appears less likely that the recognition of M-protein can account for the cross-reactivity of cytotoxic T-lymphocytes for different type A influenza viruses.