The release of TNF-α and IL-1β in contact co-cultures (M+P) and non-contact co-cultures (M/P). The co-cultures were exposed to silica (80 and 160 μg/cm2) for 43 h. Data represent means ± SE for n = 3 separate experiments. *P < 0.05 shows statistical differences of exposed co-cultures vs. control co-cultures. #P < 0.05 shows statistical differences of exposed contact co-cultures vs. exposed non-contact co-cultures. Data were log-transformed before performing ANOVA.