Increased virus titers in the lungs of MBL null mice. A, Virus titers in lung homogenates following IAV infection were assayed on days 1, 4 and 7. Three mice were used for each group at each time point. Virus titers were expressed as FFC/lung (g) ± SE. *, p < 0.005. B, Administration of rhMBL rescues susceptible phenotype of MBL null mice. MBL null mice were reconstituted with rhMBL or PBS as a control and virus titer was determined in lung homogenates at 24 hr after virus inoculation. Mice used were 7, 5 and 4 for MBL null, MBL null + rhMBL and WT mice, respectively. Virus titers were expressed as FFC/lung (g) ± SE. *, p < 0.005.