BALB/c mice are particularly well known for the production of plasmacytomas following injection with mineral oil forming the basis for the production of monoclonal antibodies. Although not all BALB/c substrains have been examined for plasmacytoma induction, substrains derived from the Andervont (An) lineage (which includes BALB/cByJ) typically are susceptible, while those descended from BALB/cJ are resistant (see: Potter M, 1985). Mammary tumor incidence is normally low but infection with mammary tumor virus by fostering to MMTV+ C3H mice dramatically increases tumor number and age of onset. BALB/c mice develop other cancers later in life including reticular neoplasms, primary lung tumors, and renal tumors. Rare spontaneous myoepitheliomas arising from myoepithelial cells of various exocrine glands have been observed in both BALB/cJ and BALB/cByJ substrains. This strain was found to be susceptible to infection by Listeria monocytogenes, with a 3 day median time to death in females (Cheers and McKenzie, 1978). White et al. reported a variation in thioglycolate medium-induced peritoneal leukocyte recruitment in 4 analyzed strains. The response of total leukocyte recruitment, from greatest to least, was C57BL/6J&gt;BALB/c&gt;CD1&gt;129X1/SvJ. Variations were also found in the timeline of response and cell types most impacted. BALB/c mice immunized with PLP180-199 develop an atypical form of experimental autoimmune encephalomyelitis (EAE) in which susceptibility is determined by location. In the spinal cord 60-70% mice develop pathological lesions and in the brain and cerebellum 100% of mice develop sever lesions. A 2022 study found vaginal septa in 16% of BALB/cJ females. Despite evidence that septa contribute to non-productive females (Cunliffe-Beamer T, Lab Anim Sci, 1976), a breeding study conducted in 2022 found minimal effects on breeding productivity. BALB/c mice are predisposed to dystrophic cardiac calcinosis (mineralization of cardiac tissues). Using <a href="https://www.jax.org/strain/001026">BALB/cByJ</a> and <a href="https://www.jax.org/strain/000651">BALB/cJ</a> mice obtained from The Jackson Laboratory, a study by the laboratory of Dr. Steven Taffet reports that BALB/cByJ mice exhibited more frequent and severe calcium deposition (44/49; 90% at 5 weeks of age) than did BALB/cJ (1/6; 17% at 5 weeks of age) or other BALB/c substrains [Glass et al. 2013 Comp Med 63: 29 (<a href="https://pubmed.ncbi.nlm.nih.gov/23561935/">PMID:23561935</a>)]. Mice may often exhibit yellow fur, particularly around genital region (presumably the result of urination stains), which may be accompanied by localized hair loss and more prominent in older mice.

BALB/cJ is a commonly used inbred. Key traits include a susceptibility to developing the demyelinating disease upon infection with Theiler's murine encephalomyelitis virus. The BALB/cJ substrain is susceptible to Listeria, all species of Leishmania, and several species of Trypanosoma, but is resistant to experimental allergic orchitis (EAO).