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Amino acid positions involved in ADCC, ADCP, CDC, half-life and half-IG exchange

• Antibody-dependent cellular cytotoxicity (ADCC)
• ADCC reduction
• ADCC enhancement
• Antibody-dependent cellular phagocytosis (ADCP)
• Complement-dependent cytotoxicity (CDC)
• CDC enhancement
• CDC reduction
• Reduced CDC and ADCC
• Half life increase
• Half-IG exchange
• B cell inhibition by coengagement of antigen and FcγR on same cell
• Hexamerisation
• Knobs-into-holes
• No glycosylation site
• Site-specific drug attachment engineered cysteine

IMGT engineered variant nomenclature has been set up for an easier comparison between engineered antibodies. The IMGT engineered variant name comprises the species, the gene name, the letter 'v' with a number, and then the domain(s) with AA change(s) defined by the letter of the novel AA and position in the domain. The IMGT engineered variants are described in the table below, classified on the effects on antibody-dependent cytotoxicity (ADCC), antibody-dependent phagocytosis (ADCP), complement-dependent cytotoxicity (CDC), half-life increase, half-IG exchange, B cell inhibition by coengagement of antigen and FcγR on same cell, and knobs-into-holes. For a list of the IGHG variants per gene, see IGHG engineered variant nomenclature: IGHG variants.
IMGT engineered variants are classified by comparison with the allele *01 of the gene and, if the effects are independent on the alleles, as a references for the description of the amino acid (AA) changes for the other alleles. In those cases, the same variant (v) number is therefore used for any allele of the same gene in the same species.
If consequences of the AA changes are different depending on alleles, the allele (identified by an asterisk followed by a number, for example *01) is included in the IMGT engineered variant nomenclature, for example IGHG1*01 instead of IGHG1.
Headers of the tables include:
IMGT gene name: based on the IMGT-ONTOLOGY CLASSIFICATION axiom.
IMGT IGHG CH domain: based on the IMGT-ONTOLOGY DESCRIPTION axiom.
IMGT amino acid (AA) changes on IGHG CH domain: described using the IMGT unique numbering for C-DOMAIN, a major concept of the IMGT-ONTOLOGY NUMEROTATION axiom.

Effects on binding, Effects on half-life, Effects on half-IG exchange, Modification of effector properties: data from the literature (references quoted).
IMGT description of AA changes on IGHG and correspondence with Eu numbering: correspondence between the IMGT description of AA changes on IGHG and the Eu numbering (between parentheses).

Antibody-dependent cellular cytotoxicity (ADCC)

ADCC reduction

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	E1.4>P	Homsap IGHG1v1 CH2 P1.4	Prevents FcγRI binding [1]		Amino acid change (Homsap IGHG2-like).	CH2 Glu E1.4>Pro P (233)
			L1.3>V	Homsap IGHG1v2 CH2 V1.3	Decreases FcγRI binding [1]		LLGG (Homsap IGHG1)>VLGG.	CH2 Leu L1.3>Val V (234)
			L1.2>A	Homsap IGHG1v3 CH2 A1.2	Prevents FcγRI binding [1]		LLGG (Homsap IGHG1)>LAGG.	CH2 Leu L1.2>Ala A (235)
			P114>A	Homsap IGHG1v4 CH2 A114		Reduces ADCC [2]	CH2 Pro P114 (329) is conserved in the four Homsap IGHG.	CH2 Pro P114>Ala A (329)
			K109>W	Homsap IGHG1v5 CH2 W109		Reduces ADCC [6]		CH2 Lys 109>Trp W (326)

ADCC enhancement

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	S85.4>A / E118>A / K119>A	Homsap IGHG1v6 CH2 A85.4, A118, A119	Increases FcγRIIIa binding [3]	Enhances ADCC [3]		CH2 Ser S85.4>Ala A (298)/Glu E118>Ala A (333)/Lys K119>Ala A (334)
			S3>D / l117>E	Homsap IGHG1v7 CH2 D3, E117	Increases FcγRIIIa binding [4]	Enhances ADCC [4]		CH2 Ser S3>Asp D (239)/lle l117>Glu E (332)
			S3>D / A115>L / I117>E	Homsap IGHG1v8 CH2 D3, L115, E117	Increases FcRIIIa binding [4] Decreases FcRIIb binding [4]	Enhances ADCC [4]		CH2 Ser S3>Asp D (239)/Ala A115>Leu L (330)/IIe I117>Glu E (332)
		CH2 and CH3	CH2 F7>L / R83>P / Y85.2>L / V88>I / CH3 P83>L	Homsap IGHG1v9 CH2 L7, P83, L85.2, I88; CH3 L83		Enhances ADCC (100% increase) [14]		CH2 Phe F7>Leu L (243)/Arg R83>Pro P (292)/Tyr Y85.2>Leu L (300)/Val V88>IIe I (305)/CH3 Pro P83>Leu L (396)
		CH2	L1.3>Y / L1.2>Q / G1.1>W / S3>M / H30>D / D34>E / S85.4>A	Homsap IGHG1v10 CH2 Y1.3, Q1.2, W1.1, M3, D30, E34, A85.4	Increases FcγIIIa binding (F158 by >2000-fold, V158 by >1000-fold) (association of H chain 1 (IGHG1*01v10) and H chain 2 (IGHG1*01v11)) [15]	Enhances ADCC [15]		CH2 Leu L1.3>Tyr Y (234)/Leu L1.2>Gln Q (235)/Gly G1.1>Trp W (236)/Ser S3>Met M (239)/His H30>Asp D (268)/Asp D34>Glu E (270)/Ser S85.4>Ala A (298)
			D34>E / K109>D / A115>M / K119>E	Homsap IGHG1v11 CH2 E34, D109, M115, E119				CH2 Asp D34>Glu E (270)/Lys K109>Asp D (326)/Ala A115>Met M (330)/Lys K119>Glu E (334)
			G1.1>A / S3>D / A115>L / I117>E	Homsap IGHG1v12 CH2 A1.1, D3, L115, E117	Increases FcγRIIIa affinity [5]			CH2 Gly G1.1>Ala A(236)/Ser S3>D(239) Ala A115>Leu L(330)/Ile I117>E(332) 5d6d FCGR3A: Fc complex
	IGHG2	CH2	VAG->LLGG (1.3 / 1.2 / 1.1 / 1)	Homsap IGHG2v1 CH2 L1.3, L1.2, G1.1, G1	Confers FcγRI binding (WT does not show any binding capacity) [1]		VAG- > LLGG (Homsap IGHG1-like)	VAG>L1.3, L1.2, G1.1, G1 (234-237)
	IGHG4	CH2	F1.3>L	Homsap IGHG4v1 CH2 L1.3	Increases FcγRI affinity [1]		FLGG > LLGG (Homsap IGHG1-like)	Phe F1.3>Leu L(234)
Mus musculus	IGHG2B	CH2	E1.2>L	Musmus IGHG2Bv1 CH2 L1.2	Increases FcγRI affinity [5]		LEGG > LLGG (Homsap IGHG1-like)

Antibody-dependent cellular phagocytosis (ADCP)

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	G1.1>A / S3>D / I117>E	Homsap IGHG1v13 CH2 A1.1, D3, E117	Increases FcγRIIa binding [16] Increases FcγRIIa/FcγRIIb binding ratio [16]	Enhances ADCP (phagocytosis of antibody-coated target cells by macrophages) [16]	CH2 Gly G1.1>Ala A (236)/Ser S3>Asp D (239)/IIe I117>Glu E (332) Variants with G1.1>A have a 70>fold greater FcγRIIa affinity and 15-fold improvement in FcγRIIa/FcγRIIb ratio [16]

Complement-dependent cytotoxicity (CDC)

CDC enhancement

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	K109>W	Homsap IGHG1v5 CH2 W109	Increases C1q binding [6]	Enhances CDC [6]		CH2 Lys K109>Trp W(326)
			E118>S	Homsap IGHG1v15 CH2 S118	Increases C1q binding [6]	Enhances CDC [6]		CH2 Glu E118>Ser S(333)
			K109>W / E118>S	Homsap IGHG1v16 CH2 W109, S118	Increases C1q binding [6]	Enhances CDC [6]		CH2 Lys K109>Trp W (326)/Glu E118>Ser S (333)
			IgG1-G3 chimere (IGHG1 CH1-hinge - IGHG3 CH2-CH3)		Increases C1q binding [17]	Enhances CDC [17]		CH2 Lys K38>Gln Q(274)/Asn N40>Lys K(276)/Tyr Y85.2>Phe F(300)(1)
			S29>E / H30>F / S107>T	Homsap IGHG1v17 CH2 E29, F30, T107	Increases C1q binding [18]	Enhances CDC [18]		CH2 Ser S29>Glu E (267)/His H30>Phe F (268)/Ser S107>Thr T (324)
			S29>E	Homsap IGHG1v35 CH2 E29	Increases C1q binding [18]	Enhances CDC [18]		CH2 Ser S29>Glu E (267)
		CH3	CH3 E1>R / E109>G / S120>Y favors IgG1 hexamerization	Homsap IGHG1v18 CH3 R1, G109, Y120	Increases C1q binding [19]	Enhances CDC [19]		CH3 Glu E1>Arg R (345)/Glu E109>Gly G (430)/Ser S120>Tyr Y (440) (the triple mutant IgG1-005-RGY (IGHG1v18) form IgG1 hexamers) [19]
	IGHG4	CH2	S116>P	Homsap IGHG4v2 CH2 P116		Enhances CDC [8]	P116 is found in Homsap IGHG1, IGHG2, and IGHG3, that is in the IGHG other than IGHG4

CDC reduction

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	D34>A	Homsap IGHG1v19 CH2 A34	Reduces C1q binding [2]	Reduces CDC [2]	CH2 Asp D34>Ala A (270)
			K105>A	Homsap IGHG1v20 CH2 A105	Reduces C1q binding [2]	Reduces CDC [2]	CH2 Lys K105>Ala A (322)
			P114>A	Homsap IGHG1v4 CH2 A114	Reduces C1q binding [2]	Reduces CDC [2]	CH2 Pro P114>Ala A (329)
			S3>D / A115>L / I117>E	Homsap IGHG1v8 CH2 D3, L115, E117		Ablates CDC [4]	CH2 Ser S3>Asp D (239)/Ala A115>L (330)/ Ile I117>Glu E (332)
Mus musculus	IGHG2B	CH2	E101>A	Musmus IGHG2Bv2 CH2 A101	Reduces C1q binding [7]	Reduces CDC [7]	CH2 E101, K103 and K105 form a common core in the interactions of IgG and C1q [7]
			K103>A	Musmus IGHG2Bv3 CH2 A103	Reduces C1q binding [7]	Reduces CDC [7]	CH2 E101, K103 and K105 form a common core in the interactions of IgG and C1q [7]
			K105>A	Musmus IGHG2Bv4 CH2 A105	Reduces C1q binding [7]	Reduces CDC [7]	CH2 E101, K103 and K105 form a common core in the interactions of IgG and C1q [7]

Reduced CDC and ADCC

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	L1.2>E	Homsap IGHG1v23 CH2 E1.2	Reduces C1q binding [20] Reduces FcγR binding [20]	Reduces CDC [20] Reduces FcγR effector properties [20]		CH2 Leu L1.2>Glu E (235)
			L1.3>A / L1.2>A	Homsap IGHG1v14 CH2 A1.3, A1.2	Reduces C1q binding [21] Reduces FcγR binding [21]	Reduces CDC [21] Reduces FcγR effector properties [21]		CH2 Leu L1.3>Ala A (234)/Leu L1.2>Ala A (235)
			N108>S / L113>F	Homsap IGHG1v38 CH2 S108, F113	Abrogates C1q and FcγRIII binding, increases FcγRII binding, retains FcγRI high affinity binding [35]		anti-TLR4 Hu 15C1 humanized mAb [35]	CH2 Asn N108>Ser S (325)/Leu L113>Phe F (328)
			L1.3>F / L1.2>E / P116>S	Homsap IGHG1v39 CH2 F1.3, E1.2, S116		Reduces C1q binding [20] Reduces FcγR effector properties [24]		CH2 Leu L1.3>Phe F (234)/Leu L1.2>Glu E (235)/Pro P116>Ser S (331)
			L1.3>A / L1.2>A / P116>S	Homsap IGHG1v40 CH2 A1.3, A1.2, S116		Reduces C1q binding Reduces FcγR effector properties		CH2 Leu L1.3>Ala A (234)/Leu L1.2>Ala A (235)/Pro P116>Ser S (331)
			L1.3>F / L1.2>E	Homsap IGHG1v41 CH2 F1.3, E1.2		Reduces C1q binding [20] Reduces FcγR effector properties [24]		CH2 Leu L1.3>Phe F (234)/Leu L1.2>Glu E (235)
	IGHG2	CH2	H30>Q / V92>L / A115>S / P116>S	Homsap IGHG2v2 CH2 Q30, L92, S115, S116	Reduces C1q binding [23] Reduces FcγR binding [23]	Reduces CDC [23] Reduces FcγR effector properties [23]	IgG2m4 (IGHG2v2) is based on the G2 isotype with AA changes from G4 [23]	CH2 His H30>Gln Q (268)/Val V92>Leu L (309)/Ala A115>Ser S (330)/Pro P116>Ser S (331)
			V1.2>A / G1>A / P2>S / H30>A / V92>L / A115>S / P116>S	Homsap IGHG2v3 CH2 A1.2, A1, S2, A30, L92, S115, S116	Reduces C1q binding [24] Reduces FcγR binding [24]	Reduces CDC [24] Reduces FcγR effector properties [24] Undetectable ADCC, CDC, ADCP [24]	L92, S115 and S116, three AA changes are from G4 [24]	CH2 Val V1.2>Ala A (235)/Gly G1>Ala A (237)/Pro P2>Ser S (238)/His H30>Ala A (268)/Val V92>Leu L (309)/Ala A115>Ser S (330)/Pro P116>Ser S (331)
			IgG2-G4 chimere	eculizumab	Reduces C1q binding [22] Reduces FcγR binding [22]	Reduces CDC [22] Reduces FcγR effector properties [22]
	IGHG4	CH2	L1.2>E	Homsap IGHG4v3 CH2 E1.2	Reduces C1q binding [20] Reduces FcγR binding [20]	Reduces CDC [20] Reduces FcγR effector properties [20]		CH2 Leu L1.2>Glu E(235)
			F1.3>A / L1.2>A	Homsap IGHG4v4 CH2 A1.3, A1.2	Reduces C1q binding [21] Reduces FcγR binding [21]	Reduces CDC [21] Reduces FcγR effector properties [21]		CH2 Phe F1.3>Ala A (234)/Leu L1.2>Ala A (235)

Half life increase

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on half-life	IMGT notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	M15.1>Y / S16>T / T18>E	IGHG1v21 CH2 Y15.1, T16, E18	Increases FCGRT (FcRn) binding [30]	10-fold increase at pH 6.0 [30], 4-fold increases half-life in a cynomolgus pK study [31]. T18>E amino acid change provides 2 novel salt bridges between the Fc and ΒM2 of FCGRT IMGT/3Dstructure-DB : 4n0f, 4n0u [29]. A change of IGHG1 CH2 His H93 (310) into any other amino acid (excluding Cys) leads to an undetectable binding to FCGRT (FcRn) at pH 6.0 [29]	CH2 Met M15.1>Tyr Y(252), Ser S16>T(254), Thr T18>E(256)
		CH2-CH3	M15.1>Y / S16>T / T18>E (CH2) + H113>K / N114>F / Y116>H (CH3)	IGHG1v22 CH2 Y15.1, T16, E18, CH3 K113, F114, H116	Increases FCGRT (FcRn) binding [30]		CH2 Met M15.1>Tyr Y(252), Ser S16>T(254), Thr T18>E(256), CH3 His H113>K(433), Asn N114>F(434), Tyr Y116>H(436)
		CH3	M107>L / N114>S	IGHG1v24 CH3 L107, S114	Increases FCGRT (FcRn) binding [32] (11-fold increase in affinity at pH 6.0 [32]) Increases reduction in tumor burden in human FCGRT (FcRn) transgenic tumor-bearing mice treated with an anti-EGFR or an anti-VEGF antibody [32]	From 3D structure it is postulated that N114>S allows additional hydrogen bonds with FCGRT (FcRn) [29] IMGT/3Dstructure-DB : 4n0f, 4n0u	CH3 Met M107>Leu L(428)/Asn N114>Ser S(434)
	IGHG2	CH2	T14>Q	IGHG2v4 CH2 Q14	Increases FCGRT (FcRn) binding [10]	4-fold increase in affinity at pH6.0 (no binding at pH 7.5) [10]	CH2 Thr T14>Gln Q(250)
		CH3	M107>L	IGHG2v5 CH3 L107	Increases FCGRT (FcRn) binding [10]	8-fold increase in affinity at pH6.0 (no binding at pH 7.5) [10], ~1.8-fold increase half-life in rhesus monkey pK study	CH3 Met M107>Leu L (428)
		CH2-CH3	T14>Q + M107>L	IGHG2v6 CH2 Q14, CH3 L107	Increases FCGRT (FcRn) binding [10]	27-fold increase in affinity at pH6.0 (no binding at pH 7.5)[10], ~1.9-fold increase half-life in rhesus monkey pK study	CH2 Thr T14>Gln Q(250)/CH3 Met M107>Leu L (428)
	IGHG3	CH3	R115>H	IGHG3v1 CH3 H115	Extended half life [11]		CH3 Arg R115>His H (435)
	IGHG4	CH2	M15.1>Y / S16>T / T18>E	IGHG4v21 CH2 Y15.1, T16, E18	Increases FCGRT (FcRn) binding [30]		CH2 Met M15.1>Tyr Y(252), Ser S16>Thr T(254), Thr T18>Glu E(256)
		CH2-CH3	S16>T / V91>P + N114>A	IGHG4v22 CH2 T16, P91, CH3 A114	Increases FCGRT (FcRn) binding		CH2 Ser S16>Thr T(254), Val V91>Pro P(308), CH3 Asn N111>Ala A(434)

Half-IG exchange

Species	IMGT gene name	IMGT IGHG hinge or CH domain	IMGT amino acid changes on IGHG hinge or CH domain	IMGT engineered variant nomenclature	Effects on half-IG exchange	IMGT Notes
Homo sapiens	IGHG4	hinge	S10>P	Homsap IGHG4v5 h P10	Reduces half-IG exchange [12]	PSCP > PPCP (IGHG1-like)
		CH3	R88>K	Homsap IGHG4v6 CH3 K88	Reduces half-IG exchange [13]	FFLYSRLT > FFLYSKLT (IGHG1-like)

B cell inhibition by coengagement of antigen and FcγR on same cell

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on binding	Modification of effector properties	IMGT Notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	S29>E / L113>F	Homsap IGHG1v25 CH2 E29, F113	Increases FcγRIIb binding (400-fold) [33]	Inhibits by downstream ITIM signaling in B cells [34]	obexelimab XmAb5871	Ser S29>Glu E(267)/Leu L113>Phe F(328)

Hexamerisation

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on molecular interaction	IMGT Notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH3	E109>G	Homsap IGHG1v34			CH3 Glu 109>Gly G(430)

Knobs-into-holes

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on molecular interaction	IMGT Notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH3	T22>Y / Y86>T	Homsap IGHG1v26 CH3 Y22	Knob of knobs-into-holes interactions between the CH3 of the two different gamma1 chains [28]	The T22>Y change creates the knob	CH3 Thr T22>Tyr Y(366)
				Homsap IGHG1v31 CH3 T86	Hole of knobs-into-holes interactions between the CH3 of the two different gamma1 chains [28]	The Y86>T change, in the partner CH3 domain, creates the hole	CH3 Tyr Y86>Thr T(407)
Homo sapiens	IGHG1	CH3	T22>W / T22>S, L24>A, Y86>V	Homsap IGHG1v32 CH3 W22	Knob of knobs-into-holes interactions between the CH3 of the two different gamma1 chains	The T22>W change creates the knob	CH3 Thr T22>Trp W(366)
				Homsap IGHG1v33 S22, A24, V86	Hole of knobs-into-holes interactions between the CH3 of the two different gamma1 chains	The T22>S, L24>A, and Y86>V changes, in the partner CH3 domain, creates the hole	CH3 Thr T22>Ser S(366), Leu L24>Ala A(368), Tyr Y86>V(407)

No disulfide bridge

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG hinge or CH domain	IMGT engineered variant nomenclature	Effects on molecular interaction	IMGT Notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	hinge	C5>S	Homsap IGHG1v37 h S5	No disulfide bridge inter H-L		hinge Cys C5>Ser S(220)

No glycosylation site

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on molecular interaction	IMGT Notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	N84.4>A	Homsap IGHG1v29			CH2 Asn 84.4>Ala A(297)
Homo sapiens	IGHG1	CH2	N84.4>G	Homsap IGHG1v30			CH2 Asn 84.4>Gly G(297)
Homo sapiens	IGHG1	CH2	N84.4>Q	Homsap IGHG1v36			CH2 Asn 84.4>Gln Q(297)
Homo sapiens	IGHG4	CH2	N84.4>Q	Homsap IGHG4v36			CH2 Asn 84.4>Gln Q(297)

Site-specific drug attachment engineered cysteine

Species	IMGT gene name	IMGT IGHG CH domain	IMGT amino acid changes on IGHG CH domain	IMGT engineered variant nomenclature	Effects on molecular interaction	IMGT Notes	IMGT description of AA changes on IGHG and correspondence with Eu numbering
Homo sapiens	IGHG1	CH2	S3>C	Homsap IGHG1v27 CH2 C3			CH2 Ser S3>Cys C(239)
Homo sapiens	IGHG1	CH2	3^4 ins^C	Homsap IGHG1v28 CH2 insC3A			CH2 3^4 ins^Cys C(239^240)