Phenotype analysis of B-nude rats. A. The image shows that homozygous B-nude rats are hairless. B. Gross anatomy of thymus in wild-type SD rats and B-nude rats were showed (female, 11-week-old). There was no obvious thymic tissue in B-nude rats compared to wild-type SD rats. C, D. Spleen and thymus were isolated and weighed. Spleen size and weight of B-nude rats were similar to that of wild-type SD rats. Compared to wild-type SD rats, there is little to no thymic tissue in nude rats.