The mechanism of delayed hypersensitivity is poorly understood due in large part to limited techniques for in vitro study. With the exception of the human species, live leukocytes obtained from peripheral blood, lymph nodes, spleen, or peritoneal washings have been required to transfer delayed hypersensitivity from a sensitized donor to a normal recipient (1). Study of direct interaction betwee...

Resistance to Listeria monocytogenes was demonstrated in guinea pigs undergoing systemic delayed-type hypersensitivity reactions to bovine gamma globulin.