Seymour I. Schlager

Atomic spectroscopic evidence for the absence of a low-molecular-weight (486) antigen in RNA extracts shown to transfer delayed-type hypersensitivity in vitro

Abstract Ribonucleic acid-rich extracts obtained from the spleens or lymph nodes of guinea pigs skin test sensitive to mono-( p -azobenzenearsonate)-N-chloracetyl- l -tyrosine (ARS-NAT) (MW 486) were able to convert “nonsensitive” peritoneal exudate cells (PEC) to a state of specific immunologic sensitivity, as assessed by the cell-migration-inhibition correlate of delayed hypersensitivity. Specific inhibition of migration of RNA-treated PEC by ARS-NAT antigen was observed while no inhibition of migration occurred with RNA alone or by incubation with unrelated antigens. The RNA used to transfer sensitivity was assessed for arsenic (As) content as a chemical marker for the ARS-NAT antigen utilizing two methods: a Gutzeit As assay, and atomic absorption spectroscopy (AAS). Preliminary chemical analysis utilizing the Gutzeit assay, which detects as little as 1 μg As, failed to detect As in 3200–4800 μg of RNA or in cell suspensions from the spleen, lymph nodes, and liver of immunized guinea pigs. Further attempts to detect As utilizing AAS, where the limit of As sensitivity was 0.1 ng, failed to detect As in 250 μg to 10 mg of “ARS-NAT-sensitive” RNA, suggesting that, if As is associated with the RNA-rich extracts, it could be present in an amount of no more than 5 pg in 500 μg of RNA; this corresponds to less than 0.0000065% ARS-NAT antigen. These results suggest an informational role for the RNA extracts in our delayed hypersensitivity system, paralleling similar evidence for the action of RNA extracts in antibody systems.