TABLE 1.

Binding affinities of PIR ectodomains to various ligands

Recombinant ectodomaina	KDb
	H-2Db	HLA-G	Nogo-66
	μm
PIR-B
D1–D6	4.0 ± 1.9c (4)	2.4 ± 0.7 (3)	0.57d (1)
D1D2	29 ± 5 (3)	24 ± 4 (3)	8.5 (1)
D3–D6	NBe (1)	NDf	0.80 (1)
PIR-A
D1–D6	+g (1)	ND	6.9 (2)
D1D2	ND	ND	NB (1)
D3–D6	ND	ND	4.3 (2)

^a Recombinant extracellular Ig-like domains of PIR (see supplemental Fig. S1A).

^b Affinity was determined from the binding data fit to a bivalent analyte model for Fc fusion proteins or to a 1:1 binding model for fusion proteins without Fc.

^c Affinity values were determined from the numbers of response units with various concentrations of analytes. Data are presented as the value(s) for either a single determination, the means for two different experiments, or the means ± S.D. for three to four different experiments, the number of experiments are given in parentheses. The K_D value of PIR-B–H-2D^b binding was larger than that reported previously (6), possibly due partly to the fact that in our previous SPR analysis, we employed the H-2 α chain complexed with human β₂m to ensure the stability of the complex, and we calculated the K_D at lower concentrations of anlayte than the current analysis.

^d The K_D value is larger than that reported previously (13), possibly due to the difference in the assay methods: Atwal et al. (13) employed an enzyme-linked immunosorbent assay.

^e NB, no binding detected.

^f ND, not done.

^g Binding was detected with a fixed concentration of an analyte.