 has been demonstrated. Inhibiting glycosylation of a human IgG1, by culturing in the presence of tunicamycin, causes, for example, a 50-fold decrease in the affinity of this antibody for the FcγRI receptor present on monocytes and macrophages (Leatherbarrow et al., 1985). Binding to the FcγRIII receptor is also affected by the loss of carbohydrates on IgG, since it has been described that a nonglycosylated IgG3 is incapable of inducing lysis of the ADCC type via the FcγRIII receptor of NK cells (Lund et al., 1990).
However, beyond the necessary presence of these glycan-containing residues, it is more precisely the heterogeneity of their structure which may result in differences in the ability to initiate effector functions. Galactosylation profiles which are variable depending on individuals (human serum IgG1s) have been observed. These differences probably reflect differences in the activity of galactosyltransferases and other enzymes between the cellular clones of these individuals (Jefferis et al., 1990). Although this normal heterogeneity of post-translational processes generates various glycoforms (even in the case of monoclonal antibodies), it may lead to atypical structures associated with certain pathological conditions, such as rheumatoid arthritis or Crohn's disease, for which a considerable proportion of agalactosylated residues have been demonstrated (Parekh et al., 1985).
The glycosylation profile of the purified molecule is the consequence of multiple effects, some parameters of which have already been studied. The protein backbone of IgGs, and in particular amino acids in contact with the terminal N-acetylglucosamine (GlcNAc) and galactose residues of the mannose α-1,6 arm (aa 246 and 258 of IgGs), may explain the existence of preferential structures (galactosylation), as shown in the study carried out on murine and chimeric IgGs of different isotypes (Lund et al., 1993).
The differences observed also reveal specificities related to the species and to the cell type used for producing the molecule. Thus, the conventional structure of the N-glycans of human IgGs reveals a significant proportion of bi-antennary types with a GlcNAc residue in the bisecting position, this being a structure which is absent in antibodies produced by murine cells. Similarly, the sialic acid residues synthesized by the CHO (Chinese Hamster Ovary) line are exclusively of the α-2,3 type, whereas they are of the α
has been demonstrated. Inhibiting glycosylation of a human IgG1, by culturing in the presence of tunicamycin, cause, for case, a 50 - fold decrease in the affinity of this antibody for the FcγRI receptor present on monocytes and macrophages (Leatherbarrow et al. , 1985). bind to the FcγRIII receptor is also feign by the passing of carbohydrates on IgG, since it has been describe that a nonglycosylated IgG3 is incapable of inducing lysis of the ADCC type via the FcγRIII sense organ of NK cells (Lund et al. , 1990). 
 However, beyond the necessary presence of these glycan - containing residues, it is more precisely the heterogeneity of their social organization which may result in differences in the ability to lead up effector functions. Galactosylation profile which are variable depending on individuals (human serum IgG1s) have been observe. These differences probably reflect differences in the action of galactosyltransferases and other enzymes between the cellular clones of these individuals (Jefferis et al. , 1990). Although this normal heterogeneity of post - translational processes generate various glycoforms (even in the case of monoclonal antibodies), it may lead to atypical structures associated with certain pathological conditions, such as rheumatoid arthritis or Crohn's disease, for which a considerable proportion of agalactosylated residues have been demonstrated (Parekh et al. , 1985). 
 The glycosylation profile of the purified molecule is the consequence of multiple effects, some parameter of which have already been studied. The protein backbone of IgGs, and in finical amino acid in contact with the terminal N - acetylglucosamine (GlcNAc) and galactose residues of the mannose α-1,6 sleeve (aa 246 and 258 of IgGs), may explain the existence of preferential structures (galactosylation), as indicate in the study carried out on murine and chimeric IgGs of different isotypes (Lund et al. , 1993). 
 The differences observed also unwrap specificities related to the species and to the cell character used for produce the atom. therefore, the conventional structure of the N - glycans of human IgGs reveals a significant proportion of bi - antennary types with a GlcNAc residue in the bisecting placement, this being a structure which is absent in antibodies produced by murine cell. Similarly, the sialic acid residues synthesize by the CHO (Chinese Hamster Ovary) line are exclusively of the α-2,3 character, whereas they are of the α
 had been demonstrated. Inhiniting glycosylajiin of e human IgG1, by zulturing in the presence of tynicanycin, causes, for exampue, a 50-fold decreasw in rhe affinivg of thlf anflbody hor the FcγRI regeptor presant on monocytas aud macrophages (Leatherbarrow et al., 1985). Finding tl the FcγRIII rgceptpw is also affected by the loss of carbkhydratts on IgG, since it has been described that a nonhlycosylated IgG3 id incapable of ybducing lysir of the ADCC type via the FcγRIII receptor of NK cellr (Lunb et al., 1990).
Howgrwr, hgyond the neressarj presence of these gnycan-comtaining residmes, iv is more precisely the hxterogeneity of theit structura chich may result in dufderenwes hn tfw aciljtb tk initlatx effector runctions. Gqlactosylation profolqw which are vzriablq qepending on individuals (human serum IgC1s) gave been observed. Thesw differences probabli reflect qifferences in the activity of galactosyltransferdses ena ouhcv enxtmfs between the cellular clones of these indivysuslx (Jefferis et cl., 1990). Although thix jotial heterogengity of poat-translational prlcesses geneeates varyous glycoforms (even in the casw of monocloual antibodies), it may lead to atvpical struvtures associated with eertaih pathologifal condifkons, such as rhejmanoid arthritis or Crohn's diseafe, for whmch a considdrabke pro[ortion of agalactosylated residued havg been demonstrahed (Parekh et al., 1985).
The glycosylatmpn profile og dhe purifieb molegule is the confequence of muktiple zffectr, some parzmeters of which hwve already bagn studied. Thx protein bacjbonw of IgEr, and in partivular amiuj acuds in contact witm the ferminal N-acetyogloxosamine (GlcNAv) avd dapartose sesidues of dhe oanvpse α-1,6 xrm (aa 246 and 258 of OgGs), may explain the exiatence of preferenyiwl strucjures (galwctosylation), ss shown in the stkdy cerried out pn iurine and chimeric IgGs of dirferent idotnpes (Lund et wl., 1993).
Tme dyfferences observed also reveal specificities releted to the species and to the cell type uxtd for producmng thq molecula. Thus, the conventiobal structure of uhe N-glycans of human IfGs reeeals a significant proportion of bi-antennary types with a GlcNAc residue in tye bisxceing positikn, tnis bviny a struceure xhich is absent im antibodies produced by murine cells. Shmnlarly, the sialic acid residurs synthesized cy the CHO (Chinese Hamstsr Ovary) line are exclusively of the α-2,3 tupe, whereas they are of bhe α
has been demonstrated. Inhibiting glycosylation of a by in the of tunicamycin, causes, in affinity of this for the FcγRI present on monocytes and macrophages (Leatherbarrow al., 1985). Binding to the FcγRIII receptor is also affected by the loss carbohydrates on IgG, since it has been described that a nonglycosylated IgG3 is of lysis the type via the FcγRIII receptor of NK cells (Lund et al., 1990). However, beyond the necessary of these glycan-containing residues, it is more precisely heterogeneity of their structure may result in differences in ability initiate effector Galactosylation which variable depending on (human serum IgG1s) have been observed. These differences probably reflect differences in the activity of galactosyltransferases and enzymes between clones of individuals et 1990). Although this of post-translational processes generates various glycoforms case of monoclonal antibodies), it may lead to structures associated certain pathological conditions, such as rheumatoid or Crohn's disease, for which a considerable proportion agalactosylated residues have been demonstrated (Parekh et al., 1985). The glycosylation profile of the purified the consequence of multiple some parameters of have been The backbone of and in particular amino acids in contact with the terminal N-acetylglucosamine and galactose residues of the mannose α-1,6 arm (aa 246 of may explain the of preferential structures (galactosylation), shown the study carried out and IgGs (Lund al., The differences observed also specificities related to the species to the cell type Thus, the conventional structure of the N-glycans of IgGs reveals a significant proportion of bi-antennary with a GlcNAc residue in the bisecting position, this being a structure is absent produced by murine cells. Similarly, the sialic acid synthesized by the CHO Hamster Ovary) line are exclusively of the α-2,3 type, they of the
 has been demonstrated. InhibiTing glycosYlatiOn oF a hUmAn Igg1, by cUlturing in the pREsenCe of tunicamycin, causes, fOr exaMpLE, a 50-foLD dEcreaSe in the AFfINIty Of ThIs aNtIBoDy for The fcγRI reCeptor presEnt On Monocytes and MAcRophages (LeAthErbarrow et al., 1985). binDing to ThE FcΓrIII rEcePtor iS also aFFected By the loss Of CArbohyDRates on iGg, sInce It has been describeD ThAT a nonglycosylaTed IgG3 Is INcAPAblE of Inducing lySiS of thE aDCC typE ViA THE FcΓrIII receptor oF NK cells (LunD Et aL., 1990).
HowevEr, BeyONd the nEcessArY PreSence of thesE glyCan-contaiNing reSIdues, it IS more prEciselY thE heTeroGEnEiTy oF tHEir STrUctURe wHich may rEsUlT in diFferENCES in tHe aBiliTy to iNitiate effectOr fUnctIOns. galacTosylAtioN pRofilEs whicH are vArIable depending oN indIviduals (hUmaN sEruM IGG1s) haVE been oBseRveD. These dIfferenCEs pRoBABLy Reflect differences In THE aCtivity oF galacTOsYlTRansferaSeS anD othER EnzymEs beTWeEn the celLular cLOnEs Of these InDividuAlS (JeFfeRis et AL., 1990). AltHough tHis normaL heteROgeneity of post-TRanslational pROcESSeS GeneRatEs various glYcofORms (eVen iN ThE caSE of moNocloNaL AnTIbodies), it may lead to aTyPical sTructUres associateD with certaIN PAthologiCal cONdITions, such as rheUmatoId arthritiS Or Crohn's DiseaSe, for whiCh a considERAble propOrtIon Of aGalACToSylated residuES Have BeEn demonStrAted (ParEkh Et aL., 1985).
ThE glYcOsylation Profile oF tHe PuRiFieD moleCUle is the CoNseQuEncE of muLTiple eFfectS, somE pArAMetErs of whICh HAVe alReAdY beeN stUdIed. ThE proTEin BackbonE of IgGs, anD in PArtiCuLaR amino aCids in contact WiTh the termiNaL N-aCetylgLUCosamine (glcNAc) and galactose residUEs of the ManNose α-1,6 Arm (aA 246 and 258 of IgGS), maY explaIn tHE existEnce of PrefeReNtiAL StrucTUReS (gaLaCtosylatioN), AS shOwn in ThE stuDy carriEd out on murine and chIMerIc IgGs of diffeRenT isoTYPeS (LuND eT Al., 1993).
THe DIffEREnces observed alSo reveal spEcIFiCities relaTEd tO tHe speciEs and to The ceLL type usEd for prodUcing the mOlEculE. tHus, The conventIonal strUcture of tHE N-glyCAnS of huMan igGs reVeAls A signIficanT ProPortiOn of bi-AnTennarY typeS wIth a GlcNac residue in the bisecting PositiOn, thiS beIng a strucTurE WhiCh is absenT in aNtibodies pRodUceD by muRinE Cells. simiLArLy, tHE sialIc acID residues SYnTheSIZeD by the CHO (ChINESe HAmsteR OvARy) line Are eXclusively of the α-2,3 tYPe, whereas they aRe of THE α
 has been demonstrated. In hibiting g lycos yla tio nof a  hum an IgG1, by cu l turi ng in the presence oftunic am y cin, ca uses,  for ex a mp l e , a  5 0- fol dd ec rease  in  the af finity ofthi santibody for th e FcγRI re cep tor presentonmonocy te s a n d mac rop hages  (Leat h erbarr ow et al. ,1 985).B indingt o  t he F cγRIII receptor i s  a l so affected by  the l os s  o f car boh ydrates on  I gG, s i nce ith as b e end escribed that  a nonglyco s yla ted Ig G3  is incapa ble o fi ndu cing lysisof t he ADCC t ype vi a  the Fc γ RIII re ceptor  of  NK  cel l s(L und  e t  al . ,199 0 ).However,  b ey ond t he n e c e s sary  pr esen ce of  these glycan -co ntai n ing  resi dues,  itis  more  preci selyth e heterogeneity  oftheir str uct ur e w hi ch ma y  resul t i n d ifferen ces int heab i l i ty  to initiate effec to r fu nctions.  Galac t os yl a tion pro fi les  whi c h  arevari a bl e depend ing on in di viduals  ( humanse rum  Ig G1s)h avebeen o bserved.  Thes e  differences p r obably reflec t  d i f fe r ence s i n the activ ityo f ga lact o sy ltr a nsfer asesan d  o t her enzymes between  t he cel lular  clones of th ese indivi d u a ls (Jeff eris et al., 1990). Al thoug h this nor m al heter ogene ity of p ost-trans l a tional p roc ess esgen e r at es various gl y c ofor ms  (eveninthe cas e o f m ono clo na l antibod ies), it  m ay  l ea d t o aty p ical str uc tur es  as socia t ed wit h cer tain  p at h olo gical c o nd i t ions ,su ch a s r he umato id a r thr itis or  Crohn'sdis e ase,  f or  whicha considerabl eproportion  o f a galact o s ylated r esidues have been demon s trated(Pa rekhet a l., 1985) .
T he gly cos y lation  profi le of  t hep u rifie d mo lec ul e is the c o n seq uence  o f mu ltipleeffects, some para m ete rs of which h ave  alr e a dy  be e ns tud ie d . T h e  protein backbo ne of IgGs ,a nd  in partic u lar  a mino ac ids inconta c t withthe termi nal N-ace ty lglu c o sam ine (GlcNA c) and g alactoser esidu e sof th e m annose  α -1, 6 arm  (aa 2 4 6 a nd 25 8 of I gG s), ma y exp la in the e xistence of preferentia l stru cture s ( galactosy lat i on) , as show n in  the study  ca rri ed ou t o n  muri ne a n dchi m ericIgGs of differ e nt  is o t yp es (Lund et a l .,1993) .
T h e diff eren ces observed also reveal specifi citi e s  re lat e d to  t he species and  to  t h e  cell ty pe  used for p roducing  t h e mol ecule.  Thus,  the co n v en t ionalstru ctu re of the  N- gl y cans of  h um a n IgGs  rev ea ls a s ignifi c antp r oportion of bi-a ntenn a r y typ e s w ith a  G lcNAc r e sidu e in the b isecting po sition , th is be ing a s tr ucture  wh ic h is absen t  in antib odies  produc ed  bymur ine ce lls. S imila rly,  t hesialic ac i d  r e si du e s s ynth esize dby t he CHO (C h inese Ha mst e r Ovary )lin e are ex c lu s i vely of th e α -2,3t y pe, wherea s  the y  a r e ofthe α
 has_been demonstrated._Inhibiting glycosylation of a_human IgG1,_by_culturing in_the_presence of tunicamycin,_causes, for example,_a 50-fold decrease in_the affinity of_this_antibody for the FcγRI receptor present on monocytes and macrophages (Leatherbarrow et al., 1985)._Binding_to the_FcγRIII_receptor_is also affected by the_loss of carbohydrates on IgG,_since it_has been described that a nonglycosylated IgG3 is_incapable_of inducing lysis_of the ADCC type via the FcγRIII receptor of_NK cells (Lund et al., 1990).
However,_beyond the necessary_presence_of_these glycan-containing residues, it_is more precisely the heterogeneity of_their structure which may result in_differences in the ability to initiate effector_functions. Galactosylation profiles which are variable_depending on individuals (human serum_IgG1s) have_been observed. These differences probably_reflect differences in_the activity_of galactosyltransferases and_other enzymes between the cellular clones_of these individuals_(Jefferis et al., 1990). Although this_normal_heterogeneity of post-translational_processes_generates_various glycoforms_(even in the_case_of monoclonal_antibodies),_it may lead to atypical structures_associated_with certain pathological conditions, such as rheumatoid_arthritis or Crohn's disease,_for_which a considerable proportion_of agalactosylated residues have been_demonstrated (Parekh et al., 1985).
The glycosylation_profile of_the purified_molecule is the consequence of multiple effects, some parameters of which_have already been studied. The protein_backbone of IgGs, and_in particular_amino_acids in contact_with_the terminal_N-acetylglucosamine (GlcNAc) and galactose residues of the_mannose α-1,6_arm (aa 246 and 258 of_IgGs), may explain the_existence_of preferential structures (galactosylation), as shown_in the study carried out on_murine and chimeric IgGs of_different_isotypes_(Lund et al., 1993).
The differences_observed also reveal specificities related to_the species and_to the cell type used for producing_the_molecule. Thus, the conventional structure of_the_N-glycans of human IgGs reveals a_significant_proportion_of bi-antennary types with a_GlcNAc residue in the bisecting position,_this being a structure which is absent in antibodies_produced by murine_cells. Similarly, the sialic acid_residues_synthesized_by the CHO (Chinese Hamster Ovary) line are exclusively of_the α-2,3_type, whereas they_are of the α