BALB/cJ vs. BALB/cByJ

JAX® NOTES Issue 430, July 1987

The Jackson Laboratory maintains two substrains of BALB/c: BALB/cJ and BALB/cByJ. These substrains were separated from one another in 1935 (for strain pedigree history, see Handbook on Genetically Standardized JAX Mice).

Genetic Differences

Very few genetic differences are known between these substrains. The Qa-2 on Chromosome 17 is one gene that does differ between BALB/cJ and BALB/cByJ and involves a deletion in the BALB/cByJ genome (Mellor, A., et al., Proc. Natl. Acad. Sci., USA 82:5920, 1985). For additional variation among BALB/c substrains maintained throughout the world see The BALB/c Mouse. Genetics and Immunology, M. Potter (ed.), Current Topics in a Microbiology and Immunology 122, Springer-Verlag, 1985.

 

Ascites Production

Both BALB/cJ and BALB/cByJ mice can be used to establish ascites tumors. In 1983, Dr. William J. Mandy at the University of Texas-Austin did a limited study that indicated hybridomas produced by fusing BALB/cJ spleen cells and SP2/o cells can be propagated as ascites tumors in BALB/cByJ mice. Thirty-three of 36 (91.6%) untreated BALB/cByJ mice inoculated i.p. with 106 hybridoma cells developed ascites tumors.

The major differences observed in the establishment of ascites tumors between BALB/cJ and BALB/cByJ were:

1. It took 4-5 days longer for the BALB/cByJ to develop observable tumor masses compared to the BALB/cJ. Tumors usually develop in 10-12 days in the BALB/cJ and 14-17 days in the BALB/cByJ.
2. The tumors that developed formed predominantly solid tumors which may indicate that the BALB/cByJ strain tends to encapsulate the hybridoma lines more readily than the BALB/cJ strain.
3. After a secondary passage, the solid tumors in BALB/cByJ mice reverted to the ascites form; the antibody titers observed in the ascites fluid were comparable to that obtained from BALB/cJ.

Selection of Substrains

BALB/cByJ has since been used successfully by others as an alternative to BALB/cJ for ascites tumor production. The BALB/cByJ substrain has the advantages of a higher reproductive performance and less aggressive behavior than BALB/cJ. These factors are reflected in the greater availability and the lower price of BALB/cByJ.