Figure 4.

Migration of proIL-1β on Percoll density gradient. P1 and P2 fractions were pooled and further fractionated by centrifugation on a 25% Percoll density gradient under conditions that separate heavy-density lysosomes from lower-density endosomes. Membranes were collected from the individual fractions and tested for β-hexosoaminidase activity or analyzed by Western blot using anti-CD, anti-IL-1β, or anti-Rab7 antibodies. Fraction 1 represents the lowest density; fraction 18 is the highest density. The reactivity of proCD and CD (A), IL-1β (B), and Rab7 (C) was quantified by image digitalization and plotted as arbitrary units (a.u.); β-hexosoaminidase activity (C) is expressed as percent of total. The Western blots hybridized with anti-CD and anti-IL-1β are shown as insets in A and B, respectively. One representative experiment four is shown.