Assay of Adhesion Under Shear Stress for the Study of T Lymphocyte-Adhesion Molecule Interactions

Summary

This flow adhesion assay provides a simple, high impact model of T cell-epithelial cell interactions. A syringe pump is used to generate shear stress, and confocal microscopy captures images for quantification. The goal of these studies is to effectively quantify T cell adhesion using flow conditions.

Abstract

Overall, T cell adhesion is a critical component of function, contributing to the distinct processes of cellular recruitment to sites of inflammation and interaction with antigen presenting cells (APC) in the formation of immunological synapses. These two contexts of T cell adhesion differ in that T cell-APC interactions can be considered static, while T cell-blood vessel interactions are challenged by the shear stress generated by circulation itself. T cell-APC interactions are classified as static in that the two cellular partners are static relative to each other. Usually, this interaction occurs within the lymph nodes. As a T cell interacts with the blood vessel wall, the cells arrest and must resist the generated shear stress.^1,2 These differences highlight the need to better understand static adhesion and adhesion under flow conditions as two distinct regulatory processes. The regulation of T cell adhesion can be most succinctly described as controlling the affinity state of integrin molecules expressed on the cell surface, and thereby regulating the interaction of integrins with the adhesion molecule ligands expressed on the surface of the interacting cell. Our current understanding of the regulation of integrin affinity states comes from often simplistic in vitro model systems. The assay of adhesion using flow conditions described here allows for the visualization and accurate quantification of T cell-epithelial cell interactions in real time following a stimulus. An adhesion under flow assay can be applied to studies of adhesion signaling within T cells following treatment with inhibitory or stimulatory substances. Additionally, this assay can be expanded beyond T cell signaling to any adhesive leukocyte population and any integrin-adhesion molecule pair.

Introduction

T lymphocyte adhesion mediates a number of distinct processes in a healthy immune system,³ playing critical roles in T cell trafficking and antigen presentation. Whether during immune surveillance or an active immune response these two broad roles for adhesion are critical.⁴ The physiological signaling events of T cell-endothelial cell interactions are distinct from T cell-antigen presenting cell (APC) interactions, and therefore require distinct methods of study to best understand the signaling cascades involved. The firm adhesion of a T cell to a blood vessel wall during lymphocyte extravasation requires rapid and dynamic integrin activation. T....

Protocol

1. Plating the CHO-ICAM Cells

Note: The goal of this step is to plate the CHO-ICAM cells in the flow chambers for growth overnight with the goal of generating a confluent monolayer.

1. Maintain CHO-ICAM cells in 10 cm tissue-culture treated culture dishes in 10 ml RPMI media supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin (CHO-ICAM complete culture media) at 37 °C with 5% CO₂.
2. To collect cells, add 1 ml 0.5% trypsin-EDTA and incubate at room temperature for 1 min with gentle shaking. Neutralize the trypsin with 4 ml of media.
3. Count the CHO-ICAM cells using a hemacytometer and calculate 0....

Results

Representative results are shown from the flow adhesion assay using Jurkat and primary human CD3⁺ T cells, as indicated, stimulated with SDF-1α. The negative controls in all shown experiments are unstimulated cells. A threshold basal percent adhesion of unstimulated cells is between 5 - 10%; base adhesion notably above this range indicates a problematic experiment and suggests the start population of T cells were nonspecifically pre-activated in preparation. Fold increase .......

Discussion

In order to properly analyze T cell adhesion, the stimulant to be included in the study must be considered when choosing an in vitro method. While there are several assays to study signals leading to LFA-1 activation and ICAM-1 binding all methods are not interchangeable. A static adhesion assay¹⁰ is best suited to study T cell-APC interactions; alternatively, the shear stress method detailed here is ideal to model T cell-epithelial cell interactions. In vivo, as chemokines are presented alon.......

Materials

Name	Company	Catalog Number	Comments
T cell samples (cell line or primary)	ATCC	TIB-152	Peripheral human T cells
CHO-ICAM-1 cells	ATCC	CRL-2093
µ-Slide VI 0.4 ibiTreat	ibidi	80606
500 ml glass bottle	Fisher	FB800500
250 ml glass bottle	Fisher	FB800250
Silicone tubing 0.8 mm	ibidi	10841
Confocal microscope with incubator chamber	Ziess	700	Any wide field fluorescent microscope
Syringe pump	New Era Pump Systems	NE-300
60 ml syringe	BD	309653
CFSE	eBioscience	65-0850
SDF-1α	R&D	350-NS-010/CF
RPMI	Lonza	12-702F/12
PBS	Lonza	17-516F
Microcentrifuge	Eppendorf	5424
D-Glucose	Sigma Aldrich	G8270
PMA	Sigma Aldrich	16561-29-8
Volocity software	Perkin Elmer	Version 6.2.1
ImageJ software	NIH	Version 1.48V
Tissue-culture treated culture dishes	Falcon	353003
Trypsin-EDTA (0.25%) Phenol Red	Gibco	25200114
Heat Inactivated FBS	Denville	FB5001-H
Penicillin/Streptomycin	Fisher	BP295950