IFNγ, TNF and reactive nitrogen intermediates (RNI; measured using nitric oxide synthase (NOS-2) as a surrogate marker) are all critical for the control of L. donovani infection [9]–[11],[17], and mRNA encoding all of these molecules was significantly reduced (p<0.05) in the livers of mice receiving anti-VCAM-1 mAb (Figure 1D–F) at day 14 p.i. To confirm that VLA-4 was the main integrin interacting with VCAM-1 during VL, we also blocked this molecule using antibody over the first 14 days of infection, and obtained very similar results (Figure 2). This evidence concerns the gene TNF and infection.