CD79A and chronic obstructive pulmonary disease: One study showed a poor association (p = 0.17) between serum IgA and cervical mucosal SIgA, suggesting that the systemic humoral immune response may not be representative of the local humoral immune response.[20] The findings of this study that serum levels of IgA are associated with exacerbation risk suggest the need to better understand the link between serum and airway IgA and COPD morbidity.