<prompt> In respiratory and GIT infections, which is the most affected immunoglulin -IgAIgGIgMIgD  <response>: Immunoglobulin A is an antibody that plays a critical role in immune function in the mucous membranes. More IgA is produced in mucosal linings than all other types of antibody combined Ref: Ananthanarayan Parkers textbook of microbiology 9th edition pg:97-98 