Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Immunomodulation

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system can suddenly attack the body’s tissues—as in autoim-

mune diseases like rheumatoid arthritis, juvenile diabetes, sys-

temic lupus erythematosus, or multiple sclerosis.

The hunt continues for new vaccines, especially against

parasitic organisms like the malariamicrobe that trick the

immune system by changing their antigens. Some researchers

are seeking ways to start an immune response that prevents or

kills cancers. A big goal of immunologists is the search for a

vaccine for HIV, the virus that causes AIDS. HIV knocks out

the immune system—causing immunodeficiency—by infect-

ing crucial T lymphocytes. Some immunologists have sug-

gested that the chiefly humoral response raised by

conventional vaccines may be unable to stop HIV from getting

to lymphocytes, and that a new kind of vaccine that encour-

ages a cellular response may be more effective.

Researchers have shown that transplant rejection is just

another kind of immune response, with the immune system

attacking antigens in the transplanted organ that are different

from its own. Drugs that suppress the immune system are

now used to prevent rejection, but they also make the patient

vulnerable to infection. Immunologists are using their

increased understanding of the immune system to develop

more subtle ways of deceiving the immune system into

accepting transplants.

See alsoAIDS, recent advances in research and treatment;

Antibody, monoclonal; Biochemical analysis techniques;

BSE, scrapie and CJD: recent advances in research; History of

immunology; Immunochemistry; Immunodeficiency disease

syndromes; Immunodeficiency diseases; Immunodeficiency;

Immunogenetics; Immunological analysis techniques;

Immunology, nutritional aspects; Immunosuppressant drugs;

Infection and resistance; Laboratory techniques in immunol-

ogy; Reproductive immunology; Transplantation genetics and

immunology

IMMUNOLOGY, HISTORY OF•seeHISTORY OF

IMMUNOLOGY

IImmunology, nutritional aspectsMMUNOLOGY, NUTRITIONAL ASPECTS

The role of nutrition is central to the development and modu-

lation of the immune system. The importance of nutrition has

been made clear by the burgeoning field of sports medicine. It

appears the immune system is enhanced by moderate to severe

exercise, although many components of the immune response

exhibit adverse change for a period of from 3 to 72 hours after

prolonged intense exertion. This “window of opportunity” for

opportunistic bacterial and viral infections seems to be

increased for “elite” athletes that are more prone to over-train.

The elements of the immune response most affected by the

strenuous activity that leads to the impairment of the immune

system are lymphocyte concentrations, depressed natural

killer activity, and elevated levels of IgA in the saliva.

The possible basis for this prolonged immunosuppres-

sion may include reduced plasma glutamine concentrations,

altered plasma glucose levels, and proliferation of neutrophils

and monocytes that increases prostaglandin concentrations.

Exercise produces oxidative stress and so concomitantly, there

are elevated free radical levels along with an attendant deple-

tion of antioxidant levels. Therefore, antioxidants that help

protect against oxidative stress are considered the most prom-

ising for further study, but those nutrients that heal the gut

show potential also. These nutrients include Vitamin E,

Vitamin C, zinc, and glutamine. Glutamine and nucleotides

show a direct effect on lymphocyte proliferation. Free radicals

and other reactive oxygen species that can damage cells as

well as tissues are an integral part of the immune system, so

the body has developed systems that protect from their dam-

age. These products function by destroying invading organ-

isms and damaged tissues, as well as enhance interleukin-I,

Interleukin-8 and tumor necrosis factor concentrations as part

of the inflammatory response. The purpose of supplementing

the diet is to provide a balance to the immune system’s pro-

oxidant function. Carbohydrate supplementation has addition-

ally shown impressive results. Increased plasma levels, a

depressed cortisol and growth hormone response, fewer fluc-

tuations in blood levels of immune competent cells, decreased

granulocyte and monocyte phagocytosis, reduced oxidative

stress and a diminished pro-inflammatory and anti-inflamma-

tory cytokine response are all associated with an increase in

complex carbohydrate consumption.

Besides exercise-associated immune suppression, mal-

nutrition plays a pivotal role in modulating the immune

response. Nowhere is this more important then during preg-

nancy and gestation. Besides genetics, no other factor is more

important for the developing immune system then optimal

nutrition. The immune response of low-birth-weight babies is

compromised as well as those of children born to mothers

without adequate nutrition. Especially important is the role of

Vitamin E and selenium in preventing immune impairment.

Animal studies showed that progeny of Vitamin E and sele-

nium-deficient mothers never adequately developed immune

competent cell lines.

Because nutrition plays such a vital role in the immune

response, a special branch of immunologyis developing called

immunonutrition. These scientists are particularly interested in

the interaction of genetics and nutrition. Preliminary work

suggests that individual genotypes vary in their response to

healing, infection, and dietary supplementation.

See also Immunogenetics; Infection and resistance;

Metabolism

IImmunomodulationMMUNOMODULATION

From a therapeutic point of view, immunomodulation refers to

any process in which an immune response is altered to a

desired level. Microorganismsare also capable of modulating

the response of the immune systemto their presence, in order

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