To test this hypothesis, we used cell lines from three other tick species not considered vectors of Rp, ISE6 (Ixodes scapularis; black-legged ticks), BME26 (Boophilus microplus; cattle tick), and IRE11 (Ixodes ricinus; European sheep tick), to monitor apoptosis during the later stage of Rp infection (4 days p.i.). This evidence concerns the gene BLOC1S3 and retinitis pigmentosa 1.