Blood changes in experimental arthritis in two types of genetically different rats

1. Rats genetically resistant to dextran and other agents producing the anaphylactoid reaction (NR rats), have a higher polymorph count than do rats which react to these agents (R rats).2. NR rats do not develop polyarthritis when a hind paw is injected intradermally with Freund's adjuvant.3. The polyarthritis produced by an intravenous injection of Mycoplasma arthritidis culture develops more slowly in NR rats than in R rats.4. It is not clear whether the higher polymorph count in NR rats is a main factor in determining their resistance to adjuvant-induced arthritis.