​SecretoryImmunoglobulinA(SIgA)isasubclassofImmunoglobulinA(IgA),an antibody thatplaysacriticalroleinmucosalimmunity. SIgAisthemainimmunoglobulinfoundinmucoussecretionsfromthetearglands,salivaryglands,mammaryglands,therespiratorysystem,thegenito-urinarytract,andthegastrointestinaltract.(1)SIgAisnotsynthesizedbymucosalepithelialcellsinthesestructuresorderivedfromblood. Instead,itisproducedbyB-lymphocytesadjacenttothemucosalcells,thentransportedthroughthecellinteriors,andreleasedintothesecretionsfromthecells.(2)SIgAplaysakeyroleinprotectingvulnerableareassuchastheoralcavity,lungs,andgutfrominvADIngpathogens.(1) DifferencesinSIgAlevelsinthesalivafromdifferentglandshavebeenobservedinhumans,withthehighestlevelsfoundintheminorsalivaglands.(2,3) SIgAexhibitsadiurnalrhythm,decreasingfromthehighestlevelsinthemorningtothelowestintheevening.(4)

LevelsofSIgAinsalivavaryinresponsetophysicalandpsychologicalstressthroughinteractionswiththeautonomicnervoussystem.(5,6) SIgAlevelsinsalivaareaffectedbyflowrates,withconcentrationsnormallydecreasingasflowratesincrease. MeasurementofflowratesisadvisableinordertoexpressSIgAsecretionasafunctionoftime.(6)​

1. Holmgren,J.,Czerkinsky,C.(2005). Mucosalimmunityandvaccines. NatureMedicine,11(4Suppl),s45-53.
2. Brandtzaeg,P.(2007).Dosalivaryantibodiesreliablyreflectbothmucosalandsystemicimmunity?AnnNYAcadSci,1098,288-311.
3. Crawford,J.M.,TauBMAn,M.A.,SmithD.J.(1975). MinorsalivaryglandsasamajorsourceofsecretoryimmunoglobulinAinthehumanoralcavity. Science,190(4220),1206-9.
4. Li,T.-L.,Gleeson,M.(2004).Theeffectofsingleandrepeatedboutsofprolongedcyclingandcircadianvariationonsalivaflowrate,immunoglobulinAandalpha-amylaseresponses. JSportsSci,22(11-12),1015-1024.
5. Tsujita,S.,Morimoto,K.(1999). SecretoryIgAinsalivacanbeausefulstressMarker.EnvHealthPrevMed,4,1-8.
6. Bishop,N.C.,Gleeson,M.(2009). Acuteandchroniceffectsofexerciseonmarkersofmucosalimmunity.FrontBiosci,1(14),4444-56.