Human prealbumin fraction: Effects on cell-mediated immunity and tumor rejection

The effect of human prealbumin fraction on allogenic cell-mediated immunity in primary sensitization cultures of murine spleen cells was studied by 3H-thymidine uptake and specific 51Cr release assays. Prealbumin caused a dose-dependent augmentation of these responses. Human serum albumin, bovine serum albumin, and calf-thymosin fraction 5 had little effect. Prealbumin was active when added on day 0 or 1 but not thereafter. Prealbumin added to effector cells from immunized mice did not change their lytic activity. Prealbumin, but not human serum albumin or thymosin fraction 5, augmented secondary cell-mediated immunity in culture after primary immunization in mice. A slow growing mammary tumor line, which originated as a spontaneous mammary tumor in a DBA/2a HaDD breeder mouse, initially grows in 100% of DBA/2J mice but is then rejected in 10–20% of them. When prealbumin (50 μg/day) was given subcutaneously for 2 weeks to DBA/2J mice and the tumor implanted 2 weeks later, 78% of the mice rejected the tumor and were then resistant to a rechallenge.