Signaling lymphocytic activating molecule family member 1 (SLAMF1 or CD150) is a cell surface glycoprotein expressed on various immune populations, regulating cell-cell interactions, activation, differentiation, and inflammatory responses and has been suggested as a potential target for inflammatory diseases. Signaling is believed to be mediated by high-affinity homophilic interactions; the recombinant soluble form of SLAMF1 has optimal activity in the range of 20 μg/mL. This contradicts with a rather weak homo-dimerization binding constant (K D) value reported previously; however, the analytical approach and data analysis suffered from various technical limitations at the time and therefore warrants re-examination. To address this apparent discrepancy, we determined the K D of soluble SLAMF1 using sedimentation velocity analytical ultracentrifuge (SV-AUC). A globally fitted monomer-dimer model properly explains the data from a wide concentration range obtained with both UV and fluorescence detection systems. The analysis suggests the dimerization K D value for human SLAMF1 is 0.48 μM. Additionally, our data show that SLAMF1 self-association is not driven by non-specific binding to glycans supporting the view of specific protein-protein interaction. We anticipate antibody biotherapeutics capable of modulating the biological consequences of SLAMF1 interactions will be readily identified. [Display omitted] • The self-dimerization affinity of human SLAMF1 was determined to be 0.48 μM using analytical ultracentrifugation • This KD value is roughly 400-times tighter than a previously reported value and well supports in vivo functional observations • New data provides insight on physico-chemical properties of SLAMF1 necessary for development of antibody therapeutics • The self-association of SLAMF1 is likely driven by specific protein binding rather than non-specific glycan interactions [ABSTRACT FROM AUTHOR]