Immunopathology

immunopathology

[¦im·yə·nō·pə′thäl·ə·jē] (medicine) The study of various human and animal diseases in which humoral and cellular immune factors seem important in causing pathological damage to cells, tissues, and the host.

Immunopathology

a branch of immunology concerned with the processes arising from the harmful effects on cells and tissues of immunological reactions. Whereas humoral and cellular factors have a protective effect in immune reactions, they cause allergic and autoimmune diseases in autoaggressive processes. More exactly, the term “immunopathology” refers to diseases arising from injury to the body’s own tissues and organs under the influence of autoaggressive antibodies or sensitized lymphoid cells.

According to the modern view, autoimmune reactions may be caused by (1) sensitization by exogenous antigens that contain antigens in common with the host, (2) the influence of various external factors (infectious, chemical, physical) that alter cellular antigens, and (3) genetic changes in the lymphoid system.

In 1899, E. Metchnikoff found that erythrocytes, leukocytes, spermatozoa, and other cells injected into animals induce the formation of specific antibodies, or cytotoxins (hemolysins, leukotoxins, spermotoxins, nephrotoxins, and, in particular, autolysins). Subsequently the antigenic characteristics of the body’s own pathologically altered tissues and organs (autoallergy) were studied and the immunological processes that develop after tissue and organ transplants (tissue incompatibility) were analyzed.

A thorough investigation of the processes of immunopathology was initiated in 1939 by the German scientist F. F. Schwenker and the French scientist F. C. Comploier, who injected an animal with a kidney emulsion mixed with staphylococcal or streptococcal toxin and subsequently found antibodies against the kidneys in its blood. In 1945 the American scientists P. and E. Covelti demonstrated experimentally that injecting animals with hemolytic streptococci mixed with kidney tissue or heart tissue causes glomerulonephritis and myocarditis, respectively. Aggressive autoantibodies that appear in the process specifically injure normal kidney or heart cells and acquire the properties of autoantigens. In 1955, German scientists grouped all of these processes under the term “autoaggression.” The German scientists P. Miescher and K. O. Vordlaender regarded these processes as immunopathological (1963), while the Soviet allergologist A. D. Ado (1967) considered immunopathology to be a form of allergy.

The factors responsible for immunopathological processes are varied. Aggressive autoantibodies or sensitized lymphoid cells may be caused by exogenous factors, such as infectious agents or their toxins or the effects of frostbites, burns, and poisonings, as well as by certain internal (endogenous) factors. There are also antierythrocytic antibodies, which cause hemolytic anemias, and antilymphocytic antibodies, which cause leukopenia, leukemia, and agranulocytosis. Still other antibodies injure thrombocytes or various organs, such as the heart and kidneys. In immunopathological diseases such as allergic postvaccinal encephalitides and thyroid diseases and in organ homotransplants (that is, for example, from human being to human being), sensitized lymphoid cells play a leading role. Aggressive autoantibodies and lymphoid cells injure tissues and organs and coagulate proteins in the cells, giving rise to foreign tissue antigens or complex antigens that act on the reticuloendothelial system, where aggressive autoantibodies specific to them are formed. These antibodies are, in turn, fixed on the cells of the corresponding tissues, which are injured and die as a result.

The delicate mechanism of autoimmune reactions is the object of detailed study. Some investigators consider aggressive autoantibodies to be the dominant factor, while others emphasize the role of lymphoid cells; still others believe that it is the combining of antigen with antibody that is the basis of tissue and organ injury. It is very likely that all of these mechanisms are involved at the same time. The mechanism of the immunological reactions in organ homotransplants is to a great extent analogous to the immunopathological processes.

There will be injury to the erythrocytes (as in hemolytic anemia), the leukocytes (as in leukopenia), or the thyroid (as in Hashimoto’s thyroiditis), and so forth, depending on the altered antigens and the directivity of the autoantibodies. The formation of autoantibodies against connective tissue antigens or DNA antigens results in systemic damage to many organs (rheumatism, lupus erythematosus, and so forth).

Autoimmune disorders also develop in the irradiated organism in which radiation injury to cells and tissues changes antigenic specificity and results in the circulation of altered antigens that can bring about autoantigenic irritation, the formation of autoantibodies, and the development of autosensitization.

REFERENCES

Ado, A. D. “Allergiia ili immunopatologiia?” Vestnik Akademii meditsinskikh nauk SSSR, 1967, no. 2.
Zdrodovskii, P. F. Problemy infektsii, immuniteta i allergii, 3rd ed. Moscow, 1969.
Immunopatologiia v klinike i eksperimente iproblema autoantitel. Edited by P. Miescher and K. Vordlaender. Moscow, 1969.

A. KH. KANCHURIN and P. P. SAKHAROV

immunopathology