Molecular recognition processes between cell surface elements are discussed with special reference to cell surface pattern formation of membrane-bound integral proteins. The existence, as detected by flow cytometric resonance energy transfer (Appendix), and significance of cell surface patterns involving the interleukin-2 receptor, the T-cell receptor-CD3 system, the intercellular adhesion molecule ICAM-1, and the major histocompatibility complex class I and class II molecules in the plasma membrane of lymphocytes are described. The modulation of antigen presentation by transmembrane potential changes is discussed, and a general role of transmembrane potential changes, and therefore of ion channel activities, adduced as one of the major regulatory mechanisms of cell-cell communication. A general role in the mediation and regulation of intercellular interactions is suggested for cell-surface macromolecular patterns. The dynamic pattern of protein and lipid molecules in the plasma membrane is generated by the genetic code, but has a remarkable flexibility and may be one of the major instruments of accommodation and recognition processes at the cellular level.

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PubMedDate not supplied

Parameters to monitor aging with a possible perspective for intervention - an immunological approach.

Reliable aging markers are very rare, which are better than the chronological age or those symptoms which have such great individual variability that their scientific value is questionable. The effect of aging on immunological behavior of human (and animal) individuals is reasonably well established. In this communication an attempt is made to find an immunological marker of aging at the level of cell surface phenomena. It was observed that ion-channel activities, having a complex regulation, loose their flexible responsiveness in lymphocyte membranes during aging. A recently discovered voltage regulation of the calcium-activated potassium channels showed a distinct change with aging of human lymphocytes. A possibility to find a better marker system in complex regulatory processes is also discussed.

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PubMedDate not supplied

Aging impairs membrane potential responsiveness as well as opening of voltage and ligand gated Na+ channels in human lymphocytes.

Depolarizing effects of increasing concentrations of extracellular K(+), as well as the repolarizing effect of bretylium tosylate (BT) were evaluated in human lymphocytes from young and elderly volunteers. Cells from elderly volunteers were less responsive to depolarization induced by increased extracellular potassium concentrations than those from young volunteers. Upon a near complete depolarization induced by 140 mM K(+) in the extracellular space, a significant amount of non-responding cells were found in samples from elderly volunteers. BT, which opens the otherwise silent Na(+) channels of partially depolarized cells, with subsequent activation of the Na(+)-K(+) pump (Pieri et al., 1989). repolarized both young and old lymphocytes. However, the degree of the repolarization was only 40% in the case of lymphocytes from elderly volunteers than from that of the young. It is suggested that an increase of membrane microviscosity, characteristic of old cells, may be at least partially responsible for the decreased responsiveness of plasma membrane functions which were observed.

Journal Article↗

PubMedDate not supplied

The use of a new fluorescent viscosity indicator to study the relationship between transmembrane potential and membrane dynamics of lymphocytes.

A new fluorescent dye, polymethine derivative 4501 U, was applied to label the cytoplasmic membrane of mouse lymphocytes to investigate whether the membrane lipid dynamics is related to the transmembrane potential. The dye was found not to alter the cell viability. The dye is localized close to the external surface of the membrane, and its spectroscopic characteristics make it possible to obtain information on membrane fluidity using the intensity ratio of its two emission peaks. In contrast to recent data indicating that transmembrane potential alters the membrane lipid dynamics (as revealed by anisotropy studies with diphenyl hexatriene) 4501 U does not show such a relationship. The investigations presented support the hypothesis that the change in the transmembrane potential affects the dynamics/structure of the membrane region only at the interface between the two lipid layers.

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