Microbiology and Immunology

Alexander, Hattie Elizabeth WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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ity that vaccinationwould create “carriers,” individuals who

are not sick but who are capable of spreading the disease.

There are various vaccine treatment strategies. One

involves the injection of so-called “naked” DNA. The DNA

contains genes that code for gag, a viral component thought to

be critical to the development of AIDS. The DNA can be

attached to inert particles that stimulate the response of the

immune system. In another strategy, the viral geneis bundled

into the DNA of another virus that is injected into the patient.

As of 2002, more than two dozen experimental vaccines

intended to control, but not cure, AIDS infections are being

studied worldwide.

Treatment strategies, vaccine-based or otherwise, will

need to address the different isolates of the AIDS virus that are

present in various regions of the globe. These different isolates

tend to be separated into different geographical regions. Even

within a geographical area, an isolate can display variation

from place to place. Thus, it has become clear that a universal

treatment strategy is unlikely.

See alsoHuman immunodeficiency virus (HIV); Immune

stimulation, as a vaccine; Vaccination

ALEXANDER, HATTIEELIZABETH

(1901-1968)Alexander, Hattie Elizabeth

American physician and microbiologist

Hattie Elizabeth Alexander was a pediatrician and microbiol-

ogist who made fundamental contributions in the early studies

of the genetic basis of bacterial antibiotic resistance, specifi-

cally the resistance displayed by Hemophilus influenzae, the

cause of influenzal meningitis(swelling of the nerves in the

spinal cord and brain). Her pioneering studies paved the way

for advances in treatment that have saved countless lives.

Alexander was born in Baltimore, Maryland. She

received her B.A. degree from Goucher College in 1923. After

working as a public healthbacteriologist from 1923 to 1926,

she entered the Johns Hopkins School of Medicine. She

received her M.D. in 1930. Alexander assumed a residency at

New York City Babies Hospital in 1930. She remained there

for the remainder of her career, attaining the rank of Professor

in 1957.

Alexander pioneered studies of the antibiotic resistance

and susceptibility of Hemophilus influenzae. In 1939 she suc-

cessfully utilized an anti-pneumoniaserum that had been

developed at Rockefeller University to cure infants of influen-

zal meningitis. Until then, infection with Hemophilus influen-

zaetype b almost always resulted in death. Her antiserum

reduced the death rate by almost 80%. Further research led to

the use of sulfa drugsand other antibioticsin the treatment of

the meningitis.

In other research, Alexander established that

Hemophilus influenzaewas the cause of a malady known as

epiglottitis (also called croup). Her discovery prompted

research that has led to effective treatments for croup.

In the 1950s Alexander began studies on the genetic

basis of antibiotic resistance. During the next two decades she

made fundamental observations concerning bacterial and viral

genetics. She demonstrated that the ability of Hemophilus

influenzaeto cause disease rested with its genetic material.

Additionally she demonstrated that the genetic material of

poliovirus could infect human cells. She also proposed that the

mechanisms of inheritance of traits in microorganismscould

be similar to the mechanisms operating in humans. Time has

borne out her suggestion.

In addition to her research, Alexander devoted much

time to teaching and clinical duties. For her research and other

professional accomplishments Alexander received many

awards, honorary degrees, and other honors. Notably she

became the first woman president of the American Pediatric

Society in 1965.

See alsoBacterial adaptation; Microbial genetics

ALGAE, ECONOMIC USES AND BENEFITS•

seeECONOMIC USES AND BENEFITS OF MICROORGANISMS

AAllergiesLLERGIES

An allergy is an excessive or hypersensitive response of the

immune systemto harmless substances in the environment.

Instead of fighting off a disease-causing foreign substance, the

immune system launches a complex series of actions against

an irritating substance, referred to as an allergen. The immune

response may be accompanied by a number of stressful symp-

toms, ranging from mild to severe to life threatening. In rare

cases, an allergic reaction leads to anaphylactic shock—a con-

dition characterized by a sudden drop in blood pressure, diffi-

culty in breathing, skin irritation, collapse, and possible death.

The immune system may produce several chemical

agents that cause allergic reactions. Some of the main immune

system substances responsible for the symptoms of allergy are

the histamines that are produced after an exposure to an aller-

gen. Along with other treatments and medicines, the use of

antihistamines helps to relieve some of the symptoms of

allergy by blocking out histaminereceptor sites. The study of

allergy medicine includes the identification of the different

types of allergy, immunology, and the diagnosis and treatment

of allergy.

The most common causes of allergy are pollens that are

responsible for seasonal or allergic rhinitis. The popular name

for rhinitis, hay fever, a term used since the 1830s, is inaccu-

rate because the condition is not caused by fever and its symp-

toms do not include fever. Throughout the world during every

season, pollens from grasses, trees, and weeds produce aller-

gic reactions like sneezing, runny nose, swollen nasal tissues,

headaches, blocked sinuses, and watery, irritated eyes. Of the

46 million allergy sufferers in the United States, about 25 mil-

lion have rhinitis.

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