Acquired paternal influence in mice. Improved reproductive performance of CBA/H males immunized with rat blood cells

Adult male CBA/H mice immunized against rat blood cells displayed a significant improvement in reproductive efficiency of 50% and 26% in two breeding programmes in relation to control male breeders exposed to phosphate-buffered saline (PBS). (Both types of male were mated to normal CBA/H females.) The improvement was reflected in the significant increase in successful mating frequency and size of litters produced. The unknown mechanism of this phenomenon is discussed in relation to the known reproductive consequences of conventional genetic crosses.