Different isotype profiles ofvirus-specific antibodies inacuteand persistent lymphocytic choriomeningitis virusinfection inmice

Summary. Thehumoral immuneresponse tolymphocytic choriomeningitis virus (LCMV)wasanalysed by theuseofasensitive ELISA.Ourresults showthat LCMV carriers oftheC3Hstrain, previously believed tobecompletely tolerant tothevirus, doinfact produce LCMV-specific antibodies and,moreover, thata significant proportion oftheseantibodies belong toIgGsubclasses which areconsidered T-cell dependent. Thisfinding, together withthefact that T-cell deficient micemadelittle ornoLCMV-specific antibodies, makesitreasonable toinfer thatC3H carriers havenotonlyvirus-primed Bcells, butalso virus-primed T-helper cells. However, theisotype profiles ofthevirus-specific antibodies detected were markedly different incarriers andinimmunemice. Firstly, muchgreater inter-individual variation was observed inthecarrier population thanintheimmune mice. Secondly, inimmunemiceIgG2aantibodies dominated thehumoral response, whereas incarriers thevirus-specific activity inthis subclass wasverylow. Incontrast, LCMV-specific antibodies oftheIgG1 subclass werepresent insimilar titres inimmunemice andinthemajority ofthecarriers. Evaluation ofthe