Proinflammatory cytokine surge after injury stimulates an airway immunoglobulin a increase

Abstract

Background: : Injury stimulates an innate airway IgA response in severely injured patients, which also occurs in mice. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate the production of polymeric immunoglobulin receptor, the protein required to transport immunoglobulin A (IgA) to mucosal surfaces. Blockade of TNF-α and IL-1β eliminates the airway IgA response to injury. IL-6 stimulates differentiation of B cells into IgA-secreting plasma cells at mucosal sites. We investigated the local and systemic kinetics of TNF-α, IL-1β, and IL-6 after injury in mice. We also hypothesized that injection of exogenous TNF-α, IL-1β, and IL-6 would replicate the airway IgA response to injury.

Methods: : Experiment 1: male Institute of Cancer Research mice were randomized to uninjured controls (n = 8) or to surgical stress with laparotomy and neck incisions, with killing at 1, 2, 3, 5, or 8 hours after injury (n = 8/group). Bronchoalveolar lavage (BAL) and serum levels of TNF-α, IL-1β, and IL-6 were analyzed by enzyme-linked immunosorbent assay. Experiment 2: male Institute of Cancer Research mice were randomized to uninjured controls (n = 6), injury (surgical stress that was similar to experiment 1 except the peritoneum was left intact, n = 6), or cytokine injection with intraperitoneal injection of recombinant TNF-α, IL-1β, and IL-6. Animals were killed at 2 hours after injury, and nasal airway lavage and BAL IgA were analyzed by enzyme-linked immunosorbent assay.

Results: : Experiment 1: BAL TNF-α, IL-1β, and IL-6 levels increased in bimodal pattern after injury at 3 hours and 8 hours versus controls (p < 0.05). Serum IL-6 did not increase at 3 hours, but did show a significant increase by 5 hours versus control (p < 0.05). Serum levels of TNF-α and IL-1β did not change. Experiment 2: both Injury and combination TNF-α, IL-1β, and IL-6 cytokine injection significantly increased IgA levels in airway lavage (BAL + nasal airway lavage) compared with control (p < 0.01 for both).

Conclusions: : Airway levels of TNF-α, IL-1β, and IL-6 increase in a bimodal pattern after injury with peaks at 3 hours and 8 hours, which do not correspond to serum changes. The peak at 8 hours is consistent with the known increase in airway IgA after injury. Intraperitoneal injection of a combination exogenous TNF-α, IL-1β, and IL-6 replicates the airway IgA increase after injury. This effect is not seen with individual cytokine injections.

Figure 1

BAL concentrations of pro-inflammatory cytokines after injury * p<0.01 vs 0h, ** p<0.05 vs 0h

Figure 2

Pilot 1, airway IgA levels 8 hours after injection

Figure 3

Pilot 2, airway IgA levels 2 hours after injection

Figure 4

Pilot 3, airway IgA levels 2 hours after injection

Figure 5

Pilot 4, airway IgA 2 hours after injection

Figure 6

Pilot 5, airway IgA 2 hours after injection

Figure 7

Airway IgA levels after injury or cytokine injection p<0.05 vs control for injury and cytokines