Hormonal changes during physiological development can alter immune response to viruses and infections

October 18, 2001

Researchers Release Results of New Study, Sex Differences in Hantavirus Infection: Interactions Among Hormones, Genes and Immunity

PITTSBURGH, Pa. -- It is generally recognized among immunologists that males of all species have lower immunity than females. Men are more susceptible to a variety of infections, such as dysentery, gonorrhea, and malaria; and to certain cancers. Females are at greater risk of illnesses caused by an overactive immune system, such as systemic lupus erythematosus, diabetes ulcerative colitis, and arthritis.

Why men and women respond differently to infections caused by viruses or other parasites remains a mystery. How the immune system adopts certain strategies towards particular illnesses has not been determined. Examining gender characteristics, hormones and genes, and how they interact with immunology could provide answers to these questions. This was the goal of a team of Johns Hopkins researchers as they set out to determine how differences in sex are expressed in rats' response to hantaviruses (sex differences in hantaviruses represent an ecologically and clinically relevant model for studies of sex-based differences in infection).

Researchers Sabra L. Klein, Ph.D., A.L. Scott, and G.E. Glass, Ph.D., all from the Department of Molecular Microbiology and Immunology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, Md., have conducted a study on "Sex Differences in Hantavirus Infection: Interactions Among Hormones, Genes, and Immunity." Their findings are to be presented at the conference, Genomes and Hormones: An Integrative Approach to Gender Differences in Physiology, being sponsored by the American Physiological Society (APS) October 17-20, 2001, at the Westin Convention Center, Pittsburgh, Pa.

Methodology and Results
These researchers first set out to determine if manipulating sex steroids in adult rodents would impact the response to inoculation with the Seoul virus (a Hantavirus that naturally occurs in Norway rats). The researchers found that in the male rats, the production of antibodies increased, enhanced Th1 responses (inflammatory responses) against infection occurred, and shed or released the virus into the environment for a longer time period than comparable females in the study. Accordingly, hormone manipulation in female and male adult rodents had no effect on their normal response to virus infection.

In all animals (including humans), sex steroid hormones affect gender-specific development at two distinct times. During perinatal (i.e., during prenatal and early postnatal) development, sex steroids cause permanent, hard-wired differences in the organization of central and peripheral physiology (i.e., organizational effects). After puberty, exposure to sex steroids serves to transiently activate pre?existing hormonal circuits (i.e., activational effects). In mammals, masculine development is induced by early exposure to testosterone, whereas feminine development occurs in the absence of testosterone. Because manipulation of hormones in adult animals had no effect on responses to viral infection, these researchers hypothesized that hormones may hard-wire gender-specific immune responses earlier during development.

Therefore, the next step in the study was to determine if neonatal manipulation of sex hormones organized adult responses to the hantavirus administered to rats. After two to four days of age, male rats were castrated and females were injected with testosterone. All animals were inoculated with the Seoul virus as adults; antibody responses and viral prevalence were assessed in both sexes.

Castrated males displayed female-type responses, i.e. lower concentrations of anti-virus responses with less virus shed than in the control male population. On the other hand, injecting testosterone into female neonatal mice had no impact on that group's response to infection.

Conclusions
Altering the immune response to infection occurs at a neonatal stage, as evidenced by the lowering levels of testosterone in male mice. However, manipulating testosterone levels in female mice had no impact on the immune system. These results suggest that the preponderance of gender-related immunological diseases must be related to mechanisms other than sex steroids alone, possibly genetic differences between the sexes.
-end-
The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

***

Contact: Donna Krupa:
703.527.7357
Cell: 703.967.2751 or
djkrupa1@aol.com

Or at The APS Newsroom @
The Westin Convention Center
Pittsburgh, PA
October 17-20, 2001
Tel: 412.281.3700 (The Crawford Room)

American Physiological Society

Related Immune System Articles from Brightsurf:

How the immune system remembers viruses
For a person to acquire immunity to a disease, T cells must develop into memory cells after contact with the pathogen.

How does the immune system develop in the first days of life?
Researchers highlight the anti-inflammatory response taking place after birth and designed to shield the newborn from infection.

Memory training for the immune system
The immune system will memorize the pathogen after an infection and can therefore react promptly after reinfection with the same pathogen.

Immune system may have another job -- combatting depression
An inflammatory autoimmune response within the central nervous system similar to one linked to neurodegenerative diseases such as multiple sclerosis (MS) has also been found in the spinal fluid of healthy people, according to a new Yale-led study comparing immune system cells in the spinal fluid of MS patients and healthy subjects.

COVID-19: Immune system derails
Contrary to what has been generally assumed so far, a severe course of COVID-19 does not solely result in a strong immune reaction - rather, the immune response is caught in a continuous loop of activation and inhibition.

Immune cell steroids help tumours suppress the immune system, offering new drug targets
Tumours found to evade the immune system by telling immune cells to produce immunosuppressive steroids.

Immune system -- Knocked off balance
Instead of protecting us, the immune system can sometimes go awry, as in the case of autoimmune diseases and allergies.

Too much salt weakens the immune system
A high-salt diet is not only bad for one's blood pressure, but also for the immune system.

Parkinson's and the immune system
Mutations in the Parkin gene are a common cause of hereditary forms of Parkinson's disease.

How an immune system regulator shifts the balance of immune cells
Researchers have provided new insight on the role of cyclic AMP (cAMP) in regulating the immune response.

Read More: Immune System News and Immune System Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.