TABLE 5.

INNATE IMMUNITY: CELL TYPES, RECEPTORS AND EFFECTOR MECHANISMS

Receptors involved in M.tb uptake and signaling

• Complement receptor-3 (CR3)

• C-type lectin Dectin-1

• Fc receptors

• Scavenger receptors

• Chemokine receptors

• Mannose receptors

• DC-SIGN

• Adenosine receptor

• Toll-like receptors (TLRs) 2, 4, and 9

• Nucleotide oligomerization domains (NODs)

M.tb TLR agonists

• Lipoarabinomannan (TLR2)

• Heat shock proteins 65 and 71 (TLR2, TLR4)

• M.tb DNA (TLR9)

TLR-mediated effector mechanisms

• NF-kB activation

• Antimicrobial peptides

• iNOS, nitric oxide

• Proinflammatory cytokines

• IL-12, IL-18

Lung collectin–mediated host mechanisms

• NF-kB activation

• Expression of TLR2 and TLR4 (surfactant protein A [SP-A])

• Increase in M.tb adherence and phagocytosis (SP-A)

• Decrease in phagocytosis (SP-D)

• Limitation of intracellular growth of M.tb (SP-D)

• Increased expression of phagocytic receptors, scavenger receptor A, and mannose receptor

Definition of abbreviations: DC-SIGN = dendritic cell–specific intercellular adhesion molecule-3–grabbing nonintegrin; iNOS = inducible nitric oxide synthase; M.tb = Mycobacterium tuberculosis; NF-kB = nuclear factor-κB.