Erythrocyte-specific anti-nuclear factors in chickens of the obese strain (OS).

By indirect immunofluorescence the sera of OS chickens were shown to contain anti-nuclear factor(s) (ANF) in high frequency and at titres up to 320. Normal White Leghorn (NWL) chickens also had circulating ANF, but in low percentage and in titres up to 40 only. Neonatal OS chickens lacked demonstrable ANF. Chicken ANF could be demonstrated only if nuclei of red blood cells from birds or fish were used as antigenic substrate, but not chicken leucocytes or cryostat sections of chicken, rat or guinea-pig liver, or sections of chicken or bovine thymus. Reactivity was equal on homologous and autologous red cell nuclei. Lower titres were observed with nuclei from fish as compared with avian red cell nuclei. Absorption of chicken sera with erythrocyte nuclei of different species resulted in removal of ANF in accordance with previously established reactivity with these nuclei. In reciprocal indirect immunofluorescence blocking tests with a human SLE serum a unidirectional inhibition of chicken ANF was observed. The findings suggest that chicken ANF may be directed against a serine-rich histone fraction unique for red cell nuclei. Preliminary studies of the sera of neonatally thymectomized OS chickens revealed a significant increase in frequency and titres of erythrocyte-specific ANF by comparison with untreated birds of this strain. This supports the hypothesis that the intact thymus exerts a control function over the immunological self-recognition mechanism.