Detection of FAC protein with anti-FAC antisera. One hundred micrograms of total protein from lymphoblast cell lines was immunoblotted with anti-FAC polyclonal antibodies as described. (A) Lane 1, JY; lane 2, PD4L; lane 3, HSC536N; lanes 4 and 6, HSC536N/neo; lanes 5 and 7, HSC536N/FAC transduced with amphotropic- and GALV-pseudotyped vectors, respectively; lane 8, COS-7/neo; lane 9, COS-7/FAC. FAC protein in A was detected with FAC1 antiserum. B shows the same blot as A, after stripping and reprobing with FAN2 antiserum. (C) Immunoblot of COS-7/FAC cell lysates (10 μg total cell protein per lane) demonstrating that the strong signal observed in immunoblots with FAC1 antisera and FAN2 antisera is completely blocked by addition of purified antigen. The first lane of each set represents blocking of FAC-reactive epitopes with 20 μg purified cognate antigen in a 1-hour preincubation step with 1 μL antiserum. The second lane of each set is the unblocked positive control. Complete blocking was also possible with 10 μg antigen (data not shown).