The mononuclear‐cell response to injury

Abstract

ONE aspect of the inflammatory reaction about which little is known is the way in which the initial accumulation in the injured tissues of polymorphonuclear leucocytes becomes replaced by a similar collection of mononuclear leucocytes, i.e., lymphocytes, monocytes, macrophages and their derivatives.This transition occura whatever the cause of tissue damage, but exhibits wide differences in the rapidity of its onset, in the time taken for its completion, in the number of cells involved, both polymorph and mononuclear, and in the characteristics of the mononuclear cells. These differences are illustrated by the existence of certain infhmma tory reactions that are commonly designated "mononuclear ", because polymorph infiltration is slight and transient whereas the local accumulation of mononuclear leucocytes is maesive and persistent. In this category are the tuberculin reaction and the local leaione of typhoid fever and tuberculosis. Wide differences are known to exist also in the subsequent characteristics of the mononuclear cells. In some types of inflammation they remain lymphocybs and monocytes, in others they become transformed to macrophages, epithelioid cells, giant cells or plasma, cells. Further variation occurs in the ultimate fate of the mononuclear exudate which may disappear or be aasociatod with collagen formation or undergo the full process of organisation.The purpose of the present investigation was to investigate these problems, especially the primary one of the transformation of cellular exudates from a predominantly polymorph to a predominantly mononuclear character. To do so it was necessary to provide an effective but simple stimulus, and also in some way to label the mononuclear cells participating in the reaction so that their fate could be followed. Both these conditions were met by the use of intradermal injection of macromolecular substances. ~T H O D SIntradermal injections were made into the abdominal wall of albino rats of the Wistar strain. The solutions used were made up in sterile vessels in sterile water or isotonic saline according to the nature and concentration of the solute.The abdominal skin was sterilised with ethanol and the injection performed with a 1 ml. tuberculin syringe and no. 20 needle sterilised by boiling. The volume injected was 0.15 ml.

An alternative pathway for fibrinolysis. I. The cleavage of fibrinogen by leukocyte proteases at physiologic pH.

“…Within the confines of the vascular compartment, leukocytes frequently accumulate in complex thrombi consisting of fibrin and platelets (1)(2)(3)(4)(5); whereas in extravascular sites, the migration of leukocytes to sites of injury where fibrin has accumulated is a central feature of the inflammatory response (5)(6)(7)(8)(9). In both circumstances, the interaction of these cells with fibrin may be active rather than passive, based on the morphologic identification of fibrin within leukocytes (5)(6)(7)(8)(9), the accumulation of leukocytes in thrombi relative to their concentration in blood (4), and the demonstration that fibrinolytic activity of leukocytes is not confined to low pH, at which many cathepsins are active, but also is observed at neutral pH (10)(11)(12)(13)(14)(15)(16).…”

Human Monocytopoiesis in Acute and Chronic Inflammation

“…This statement is true except for the very early phase of the acute inflammation during which a short lasting wave of neutrophils may immigrate the site of reaction [11,12]. During acute inflammation, macrophages are exclusively recruited from blood monocytes [10,15], During chronic inflammation, the number of inflammatory macrophages at the reaction site is maintained by three different processes: (1) mon-…”

Mitogen-induced Lymphocyte and Cutaneous Reactions in Dogs

“…Since lymphokines affecting neutrophil migration and production have been described in some species [8,13], even the predomi nance of neutrophils in the lesions does not exclude this possibility. Alternatively, the lesions may represent nonspecific inflamma tion such as that reported after the injection of a variety of proteins into the skin of nonsensitized animals [12]. Against this explan ation is the small quantity of protein inject ed and the fact that these proteins are non toxic and even stimulatory to cells in vitro.…”