Immune responses of healthy humans 83-104 years of age.

The immune responses of 19 healthy people 83-104 years of age were compared to those of younger healthy persons. A decline in mitogen response to concanavalin A and pokeweed mitogen, but not to phytohemagglutinin, was observed. Positive skin test to two recall antigens occurred in only 5 of the 19 aged people; 4 of these 5 reported a history of blood transfusion. Antibody titers were elevated for persistent DNA viruses but not for RNA viruses. An excess of ABO blood type B was found, but no human leukocyte antigen (HLA)-A or HLA-B type was found in elevated proportion.