5C12 anti-FXII antibody treatment prevents the death of baboons injected with a lethal dose of HI-SA (LDSA). Survival plot of baboons treated with the anti-FXII antibody 5C12 and injected with LDSA (LDSA + 5C12, n = 4) compared with animals challenged with LDSA but lacking the 5C12 treatment (LDSA, n = 4). The survival rate of these 2 groups was determined by using the Mantel-Cox (log-rank) test. Results are significant at P < .01.