TABLE 2.

Kinetics of the albumin interactions with FcRn variants

Albumin speciesa	FcRn species	FcRn variant	ka	kd	KD	KD Reqb
			103/Ms	10−3/s	μm	μm
MSAc	Mouse	WT	4.2 ± 0.5	39.4 ± 3.1	9.3 ± 0.4	NDd
MSAc	Human	WT	3.8 ± 0.0	3.1 ± 0.1	0.8 ± 0.2	ND
HSAb	Mouse	WT	NAe	NA	NA	86.2 ± 4.1
HSAf	Human	WT	2.7 ± 1.3	12.2 ± 5.9	4.5 ± 0.1	4.6 ± 0.5
HSAb	Mouse	L166R/G167E	NA	NA	NA	26.8 ± 0.1
MSAc	Human	R164L/E165G	0.7 ± 0.1	3.4 ± 0.1	4.8 ± 0.1	ND
MSAc	Mouse	L166R/G167E	2.7 ± 0.2	18.5 ± 0.5	6.8 ± 1.8	ND
HSAc	Human	R164L/E165G	3.2 ± 0.1	26.3 ± 0.2	8.2 ± 0.1	ND

^a Dilutions of MSA and HSA were injected over immobilized receptor as shown in Figs. 5 and 8.

^b The steady-state affinity constant was obtained using an equilibrium (Req) binding model supplied by the BIAevaluation 4.1 software. The kinetic values represent the average of triplicates.

^c The kinetic rate constants were obtained using a simple first-order (1:1) bimolecular interaction model.

^d ND, not determined.

^e NA, not acquired because of fast kinetics.

^f The kinetic values have been published in Ref. 10.