Chapter 16. Adhesion of cells

P. Bongrand
Laboratoire d'Immunologie, Hôpital de Sainte-Marguerite,
BP29, 13277 Marseille Cedex 09, France

1. Introduction

Cell adhesion is a fascinating process. First, it plays a key role in many situations of biological and medical interest. Secondly, it is probably the best cell function to be considered for biophysical modeling from the micrometer to the molecular level. Thirdly, studying the biophysical aspects of cell adhesion leads to face many important problems of physics and physical chemistry as well as cell physiology.

There are at least two ways of approaching the problem of cell adhesion. A first strategy would be to perform a thorough study of a simplified model likely to share some fundamental properties with biological systems. Far reaching results were obtained along this line by studying adherence-induced deformations of individual conjugates made between lipid vesicles and/or red cells of known mechanical properties [28, 66]. As another example, detailed studies of the motion of antibody-coated red blood cells in controlled hydrodynamic flow yielded important information on the formation and rupture of intercellular bonds [169].

The aforementioned approaches yielded very useful data, and improved both biological and physical knowledge. However, several parameters likely to influence the adhesive properties of nucleated cells cannot be explored with model vesicles or even erythrocytes. Thus, the lateral displacements of adhesion molecules depend on cytoskeletal constraints [168] and active cell processes [176] that are clearly quite different in blood leukocytes and red cells. Further, whereas erythrocytes are fairly smooth at the submicrometer level, nucleated cells are studded with a variety of protrusions, blebs, ruffles, microvilli or lamellipodia with complex mechanical behavior and an obvious influence on adhesive interactions [129]. It seems therefore warranted to study biologically relevant models with available experimental and theoretical tools, even if data interpretation is less clearcut than with simpler systems. Indeed, understanding cell adhesion first requires that we identify the key parameters influencing this process and obtain reliable order-of-magnitude estimates for them.

The aim of the present review is to gather biological and biophysical data that are widely scattered in the literature, in order to allow biophysicists with a general knowledge of cell biology to assess the relevance of current physical concepts to cell adhesion. Hopefully, this might be useful to anyone willing to start research in this field. Therefore, we refer the reader to other reviews for a basic description of intermolecular forces [98] and their relevance to biological systems [22-24] as well as methods for studying cell adhesion [42].

First, we shall discuss some biological models of cell adhesion (with a bias related to the author's field of interest) in order to convey a quantitative feeling for the phenomena we are willing to study.  Secondly, we shall review some experimental data that may help build a working model of the basic 'adhering cell'.

Thirdly, we shall discuss the sequential steps of cell adhesion and current physical theories that are relevant to the involved mechanisms.

[Full text] (PDF 430 Kbytes)