Abstract: Methods for identification of exchangeable MHC binding peptides are provided herein. Their use in proto-antigen-presenting surfaces and related kits, methods, and uses are also described. The proto-antigen-presenting surface can comprise a plurality of primary activating molecular ligands comprising a major histocompatibility complex (MHC) molecule configured to bind to a T cell receptor (TCR) of a T cell and a plurality of co-activating molecular ligands each including a TCR co-activating molecule or an adjunct TCR activating molecule, wherein an initial peptide is bound to the MHC molecules. Proto-antigen-presenting surfaces can be used to rapidly prepare antigen-presenting surfaces comprising one or more peptide antigens of interest by contacting the proto-antigen-presenting surface in the presence of an exchange factor and with one or more peptide antigens so as to displace the initial peptide.

Abstract: Apparatuses and methods are described for the use of optically driven bubble, convective and displacing fluidic flow to provide motive force in microfluidic devices. Alternative motive modalities are useful to selectively dislodge and displace micro-objects, including biological cells, from a variety of locations within the enclosure of a microfluidic device.

Abstract: Methods, systems and kits are described herein for detecting the results of an assay. In particular, the methods, systems and devices of the present disclosure rely on a difference between the diffusion rates of a reporter molecule and an analyte of interest in order to quantify an amount of analyte in a microfluidic device. The analyte may be a secreted product of a biological micro-object.