Conjugation of DNA to erythrocytes

DNA was conjugated to sheep red blood cells (SRBC) by chemical methods using CrCl3, poly-L-lysine or methylated bovine serum albumin as conjugation agents and by a physical method where conjugation was accomplished by incubation at 45 degrees C. The degree of conjugation was estimated using 32P-DNA (mean size 1 kbase pairs). Employing the CrCl3 method 5.8 +/- 3.6 micrograms DNA were conjugated per 10(8) SRBC at a concentration of 70 micrograms DNA/10(8) cells. At the same DNA concentration in the incubation medium 3.0 +/- 0.6 microgram DNA/10(8) cells were conjugated by poly-L-lysine, 4.1 +/- 0.8 microgram DNA/10(8) cells by methylated bovine serum albumin and approximately 4 micrograms DNA/10(8) cells when the cells were incubated at 45 degrees C. Cells conjugated with DNA by CrCl3 showed linearly increasing conjugation with increasing concentration of DNA. Cells conjugated by poly-L-lysine (pLL) or methylated bovine serum albumin seemed to be saturated by DNA at 30 micrograms DNA per 10(8) cells. At 45 degrees C the spontaneous adhesion of DNA to SRBC increased in the concentration range investigated. The degree of conjugation of DNA to SRBC was influenced by pH, and Ca2+.pLL-conjugated DNA-SRBC, but none of the other preparations were lysed in a hemolytic assay using anti-DNA antiserum from a patient with systemic lupus erythematosus.