Lymphocyte antigen 64 homolog, radioprotective 105-kDa gene (LY64) encodes LY64, a leucine-rich repeat molecule expressed on B-cell surfaces. This gene has a striking similarity to Toll-like receptor 4 (TLR4). An extracellular molecule MD-1 is required for LY64 to signal LPS presence, as MD-2 is required for TLR4. B-cells lacking LY64 are severely impaired in LPS-induced proliferation and antibody production (Miyake et al., 2000; Nagai et al., 2002). The mouse and human LY64 was mapped to chromosome 13D1 and 5q12respectively (Miura et al., 1996). The mapping of porcine LY64 will help in investigation of its role in disease resistance of the innate immune system. Materials and methods