Reversal of metabolic block in TPI deficiency by exogenous rabbit muscle TPI (RTPI). Lymphoblastoid cells derived from TPI-deficient patients A, B, and C, a heterozygote, D, and a normal subject were cultured in serum-free medium with or without exogenous RTPI (50 U/mL) for 24 hours. Changes in intracellular enzyme activity and DHAP level were measured as described in Materials and Methods. Statistical significance: *P < .05, **P < .01, ***P < .001; NS, not significant.