IGHG3 and susceptibility to pneumonia measurement: In comparison, mice had lower titers of IgG1 in the first weeks after injury,42,61 but titers returned to normal during chronic recovery.61 Notably, IgG2 and IgA, the titers related to pneumonia and mucosal infections,142,153 are increased in people with SCI, yet IgG1, IgG3, IgG4, and IgM titers remain unchanged.