Ig seen in breast milk & secretions:

Ans: a (IgA) Ref: Ananthanarayan, 7th ed, p. 88, 89Serum IgA is the major Ig in colostrums, saliva & tears.It is concentrated in secretions and on mucus surfaces forming an antibody paste.It is important in immunity against respiratory & intestinal pathogens.Properties of Immunoglobulins:IgMIgG* Maximum intravascular concentration* Maximum molecular weight* Maximum sedimentation co efficient* Earliest Ig by the foetus* Increased in primary immune response* Activate classical pathway* Mediates hypersensitivity pneumonitis* Maximum serum concentration* Longest half life (23 days)* Only Ig to cross placenta* Ig to increase in secondary immune response* Fixes complement by classical pathway (except IgG4) IgAigE* Secreted by seromucinous glands* Ig present in milk. (Other one is IgG)* Fix complement by Alternate Pathway* Mediator of type 1 HS* Only heat labile Ig* Shortest half life (2 days), least amount in serum* Maximum carbohydrate concentration* Shows homocytotropism* Mediate Prausnitz Kustner reaction.* Ig's activating alternate pathway - IgG4, IgA, IgD* IgG in multiple myeloma, IgM in Waldenstrom's macroglobulinemia* Ig dimer is IgA. Ig pentamer is IgM