Fluid Mechanical Properties of Flow Cytometers and Assessment Cell-Cell Adhesion Forces

Abstract

The work described here originates from an effort aimed at analyzing the molecular basis of cell-cell adhesion between T lymphocytes and antigen-presenting cells. Classical techniques used by cell biologists and immunologists to “measure” cell-cell adhesion are based on counting conjugates⁽¹⁾ and assume that the extent of conjugate formation reflects the adhesion “efficiency”; flow cytometric versions of this conjugate-counting approach have already been used [Segal 1984; Shaw 1986]. While studying the adhesion between human peripheral resting T cells and B cells, we reproducibly failed, in all flow cytometers tested thus far, to detect conjugates that could be seen otherwise under the microscope; this led us to surmise that flow cytometers could disrupt fragile conjugates. In the first section, we describe the mechanical stress to which cells are subjected when being analyzed in standard flow cytometers.