Characterization of four new monoclonal antibodies that recognize mouse natural killer activation receptors.

With the aim of identifying natural killer (NK) activation receptors, we immunized BALB/c mice with (BALB/cxB6)F1 NK LAK cells and made B-cell hybridomas. These were screened for monoclonal antibody (MAb) reacting with an NK activation receptor by using an antibody-induced redirected lysis (AIRL) assay against FcR-bearing P815 targets. Four hybridomas, clones 1C10, 1F10, 2D10 and 4G4, were selected for further characterization. Protein G-purified MAbs from these clones activated both resting and IL-2 activated B6 or F1 NK cells in the AIRL assay. 1F10 MAb, but not the other three MAbs, could compete for the binding of anti-NK1.1 (PK136) MAb to F1 NK cells. The four MAbs were screened for their ability to bind to or activate NK cells from the mouse strains SJL/J, DBA/2, 129/J, C3H/J, and BALB.K. None showed activity except IC10, which could bind to and activate SJL/J NK cells. When members of the NKR-P1 family from both B6 mice (A, B, and C genes expressed) and SJL mice (only A and B genes expressed) were expressed in Jurkat cells and tested for their antibody reactivity, PK136 MAb was found to recognize B6 NKR-P1C and SJL/J NKR-P1B; IC10 MAb was found to recognize NKR-P1-A, -B and -C from B6, but not NKR-P1A or -B from SJL/J; and 1F10 MAb was found to react only with B6 NKR-P1C.