INCREASED SERUM HLA CLASS-I MOLECULE LEVELS IN ELDERLY HUMAN RESPONDERS TO INFLUENZA VACCINATION

Increased cell surface expression and serum levels of HLA class I mole cules have been shown to occur in normal elderly humans. Elderly subje cts (65 years and older) generally also have a poorer response to infl uenza vaccine than younger adults. Some 30 to 40% of elderly subjects do not respond to influenza vaccination. Sera from 20 elderly subjects with a positive response to influenza vaccine (HAI antibody titer > 4 0) and 20 subjects who did not respond (HAI antibody titer < 40) were randomly selected and the levels of soluble HLA class I molecules dete rmined before and after vaccination. The subjects who responded had hi gher serum HLA class I levels both before and after vaccination than d id non-responders. Two weeks after vaccination non-responders showed s imilar serum HLA class I levels (1.78 mg/ml+/-0.62) as compared to pre vaccination levels (1.73 mg/ml+/-0.49). The responders showed signific antly higher levels of soluble HLA class I molecules following vaccina tion (2.64 mg/ml+/-0.99) as compared to pre-vaccination (2.08 mg/ml+/- 0.85, p=0.00001). Our results suggest that measuring soluble HLA class I molecules in the serum may be useful in assessing the adequacy of r esponse to influenza vaccination in the elderly population.