TLR4 and dry eye syndrome: Direct comparison of the transcript levels of PRRs in KC, pDC, and cDC reveals that while TLR3 is expressed at similar levels in all cells, MAVS is preferentially in KCs, TLR4 and TLR8 are expressed at higher levels in cDCs, and TLR7-TLR9 are preferentially expressed by pDCs [22].