AM are important phagocytes and express many scavenger receptors. The microarray experiments indicated that PR/8 infection also significantly decreased mRNA levels of many macrophage receptors especially at 24 hpi (Table 2 and Data S1). We, therefore, investigated the impact of influenza infection on expression of scavenger receptors by real-time RT-PCR. Consistent with the results from microarray experiments, PR/8 infection significantly decreased the mRNA levels of CLEC7A (Dectin 1), macrophage scavenger receptor 1 (MSR1), CD36, and the mannose receptor C type 1 (MRC1) but did not change the expression of MRC2. However, we were not able to confirm the decrease of MARCO, due to the large variation in responses among different donors ( Figure 6A ). To further investigate if the decrease in macrophage receptor expression was associated with functional consequences, we evaluated the uptake of zymosan, which are yeast walls recognized by CLEC7A, and heat-killed S. aureus. As shown in Figure 6B , PR/8 infection reduced uptake of zymosan by AM at 24 hpi in a dose dependent manner. We did not observe a significant cell loss or cytopathic effect at 24 or 48 hpi, although most cells were infected as seen in Figure 3A -C. In addition, PR/8 infection did not affect uptake of heat-killed S. aureus until 72 hpi, when the infection induced a significant cytopathic effect (data not shown).