Spleen, lymph node, and thymus cells from CD44 gene mutated mice lack surface expression of CD44. Lymph node cells, spleen cells, and thymocytes were stained with anti-CD44 KM81 supernatants and secondary labeled with PE-conjugated goat antirat, PE-conjugated anti-CD44 KM201, or PE-conjugated anti-CD44 IM 7.8.1 (pgp-1). Mice with homozygous disruptions in the CD44 gene show no detectable surface expression. FCM data were collected for viable lymphocytes according to side scatter (SSC) and foreward scatter (FSC).