Figure 1.

MAdCAM-1 and HIV-1 gp120 bind to α₄β₇ in a cation dependent manner. (a) α₄β₇ expression detected by flow cytometry on freshly isolated primary B cells by an anti-β₇ and anti-α₄β₇ (Act-1). (b) Variability of α₄β₇ expression on B cells from two separate donors. Flow cytometry shows that the binding of R66M gp120 (derived from a patient within the first month of infection) is proportional to β₇ expression. β₇ gating is based on an isotype control for each donor. (c) Binding of R66M gp120 to α₄β₇ on B cells. R66M gp120 binding to B cells in the presence of Ca²⁺/Mn²⁺ +/− anti-α₄ (2B4), or in the absence of Ca²⁺/Mn²⁺ (EDTA buffer). MAdCAM-1 binding to B cells in the presence of Ca²⁺/Mn²⁺ +/− anti-α₄ (2B4). Values reported indicate % of binding normalized to R66M (or MAdCAM-1) binding (100%), and are derived from 3 independent donors, p<0.0001 (one way ANOVA) (R66M n=3) (MAdCAM-1 n=2). (d) Comparison of the α₄β₇-reactivity of a panel of five recombinant gp120 preparations. α₄β₇-reactivity is reported as mean fluorescence intensity (MFI) of gp120s. An unlabeled anti-α₄ (2B4) was included as a specificity control. Results are representative of at least three independent experiments using B cells from different donors.