How biological differences between men and women alter immune responses and affect women's health
Birmingham (The Conversation): Most people will have heard the term "man flu", which refers to men's perceived tendency to exaggerate the severity of a cold or a similar minor ailment.
What most people may not know is that, generally speaking, women mount stronger immune responses to infections than men.
Men are more susceptible to infections from, for example, HIV, hepatitis B, and Plasmodium falciparum (the parasite responsible for malaria).
They can also have more severe symptoms, with evidence showing they're more likely to be admitted to hospital when infected with hepatitis B, tuberculosis, and Campylobacter jejuni (a bacteria that causes gastroenteritis), among others.
While this may be positive for women in some respects, it also means women are at greater risk of developing chronic diseases driven by the immune system, known as immune-mediated inflammatory diseases.
Here we will explore how biological factors influence immune differences between the sexes and how this affects women's health.
While we acknowledge that both sex and gender may affect immune responses, this article will focus on biological sex rather than gender.
Battle of the sexes
There are differences between the sexes at every stage of the immune response, from the number of immune cells, to their degree of activation (how ready they are to respond to a challenge), and beyond.
However, the story is more complicated than that. Our immune system evolves throughout our lives, learning from past experiences, but also responding to the physiological challenges of getting older.
As a result, sex differences in the immune system can be seen from birth through puberty into adulthood and old age.
Why do these differences occur? The first part of answering this question involves the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. The X chromosome contains the largest number of immune-related genes.
The X chromosome also has around 118 genes from a gene family that are able to stop the expression of other genes, or change how proteins are made, including those required for immunity.
These gene-protein regulators are known as microRNA, and there are only two microRNA genes on the Y chromosome.
The X chromosome has more genes overall (around 900) than the Y chromosome (around 55), so female cells have evolved to switch off one of their X chromosomes. This is not like turning off a light switch, but more like using a dimmer.
Around 15-25 per cent of genes on the silenced X chromosome are expressed at any given moment in any given cell.
This means female cells can often express more immune-related genes and gene-protein regulators than males. This generally means a faster clearance of pathogens in females than males.
Second, men and women have varying levels of different sex hormones.
Progesterone and testosterone are broadly considered to limit immune responses.
While both hormones are produced by males and females, progesterone is found at higher concentrations in non-menopausal women than men, and testosterone is much higher in men than women.
The role of oestrogen, one of the main female sex hormones, is more complicated. Although generally oestrogen enhances immune responses, its levels vary during the menstrual cycle, are high in pregnancy and low after menopause.
Due in part to these genetic and hormonal factors, pregnancy and the years following are associated with heightened immune responses to external challenges such as infection.
This has been regarded as an evolutionary feature, protecting women and their unborn children during pregnancy and enhancing the mother's survival throughout the child-rearing years, ultimately ensuring the survival of the population.
We also see this pattern in other species including insects, lizards, birds and mammals.
What does this all mean?
With women's heightened immune responses to infections comes an increased risk of certain diseases and prolonged immune responses after infections.
An estimated 75-80 per cent of all immune-mediated inflammatory diseases occur in females.
Diseases more common in women include multiple sclerosis, rheumatoid arthritis, lupus, Sjogren's syndrome, and thyroid disorders such as Graves disease.
In these diseases, the immune system is continuously fighting against what it sees as a foreign agent.
However, often this perceived threat is not a foreign agent, but cells or tissues from the host. This leads to tissue damage, pain and immobility.
Women are also prone to chronic inflammation following infection.
For example, after infections with Epstein Barr virus or Lyme disease, they may go on to develop chronic fatigue syndrome, another condition that affects more women than men.
This is one possible explanation for the heightened risk among pre-menopausal women of developing long COVID following infection with SARS-CoV-2, the virus that causes COVID.
Research has also revealed the presence of auto-antibodies (antibodies that attack the host) in patients with long COVID, suggesting it might be an autoimmune disease.
As women are more susceptible to autoimmune conditions, this could potentially explain the sex bias seen.
However, the exact causes of long COVID, and the reason women may be at greater risk, are yet to be defined.
This paints a bleak picture, but it's not all bad news. Women typically mount better vaccine responses to several common infections (for example, influenza, measles, mumps, rubella, hepatitis A and B), producing higher antibody levels than men.
One study showed that women vaccinated with half a dose of flu vaccine produced the same amount of antibodies compared to men vaccinated with a full dose.
However, these responses decline as women age, and particularly after menopause.
All of this shows it's vital to consider sex when designing studies examining the immune system and treating patients with immune-related diseases.
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Trump arrives in China for talks with Xi
Beijing (PTI): US President Donald Trump arrived in China on Wednesday for a three-day state visit during which he will discuss a host of global issues, including the Iran war, with Chinese President Xi Jinping.
Trump, who is visiting China at the invitation of President Xi, was received by Chinese Vice President Han Zheng at the airport.
The leaders of the world's two largest economies will hold their seventh face-to-face talks. They last met face-to-face in October 2025 in Busan, South Korea.
The US President arrived in China on his second visit in nine years to clinch a trade deal, to end the frictions over tariffs that affected its over USD 525 billion exports to the US.
Trump, who is accompanied by top CEOs, was the last US president to visit China in 2017, during his first term.
President Trump would have a bilateral meeting with Xi on Thursday, US Principal Deputy Press Secretary Anna Kelly said on Sunday.
The two leaders will meet again on Friday for a bilateral tea and working lunch, she said, adding that the US plans to host the Chinese leader for a reciprocal visit later this year.
Ahead of Trump's arrival, Chinese Vice-Premier He Lifeng and Scott Bessent completed the final round of trade negotiations in South Korea, details of which are not known.
The talks focused on trade and tariffs, Artificial Intelligence and technology, Taiwan and US' arms sales to Taipei, Iran and West Asia security and rare earths and supply chains.
Trump's schedule included a visit to the Temple of Heaven, a complex of imperial temples where emperors would pray for a good harvest.
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Ahead of his departure for Beijing, Trump told the media in Washington he would be talking with Xi about trade more than anything else.
He plans to sign more deals with China to buy more American food and aircraft. The two countries also plan to set up a Board of Trade with China to address differences between the countries.
From a trade point of view, China looks to reap a rich harvest as Trump is accompanied by top CEOs of US multinational giants, including Tesla chief Elon Musk and Apple CEO Tim Cook, who have well-entrenched business in China.
Apple has regained the top spot in China's competitive smartphone market as of early 2026, driven by a 28 per cent surge in iPhone shipments.
In April, Tesla's China-made vehicle sales (including exports) reached 79,478, a 36 per cent year-over-year increase, signalling a production rebound.
The top US business leaders will be allowed to mingle with their Chinese counterparts at an exclusive international business club, according to Chinese officials.
The global focus on the summit, however, would be on any possible outcome that could end the US-Israeli-Iran war and end the blockade of the Strait of Hormuz.
Ahead of Trump's visit, Iranian Foreign Minister Abbas Araghchi made his first visit to Beijing after the war and held talks with his Chinese counterpart Wang Yi.
The US watched his visit closely as China is the largest importer of Iranian oil and shares strategic defence ties with Tehran, and has considerable influence over Iran.
After talks with Araghchi, Wang called on Iran to reopen the Strait of Hormuz as soon as possible, even as it appreciated Tehran's commitment not to develop nuclear weapons, a prime demand of Trump to end the war.
Commenting on Wang-Araghchi talks, US Secretary of State Marco Rubio said, "I hope the Chinese tell him what he needs to be told. And that is what you are doing in the Strait, which is causing you to be globally isolated. You're the bad guy in this."
China's anxieties over the Gulf war increased, especially after Trump imposed a blockade of Iranian ports, restricting Iran's oil exports to China.
Bert Hoffman, former World Bank country director for China, said China wants the Iran war to end because it has many partners in the region, including Saudi Arabia, the UAE and Kuwait. "So they don't like to see wars, they like to have stability," he said.
In its editorial on Trump's visit, state-run Global Times said Xi has held multiple telephone conversations and meetings with him, which have helped correct the course of the bilateral relationship and steer it clear of hidden dangers at critical moments.
For China-US relations to truly stabilise and improve in the future, the most fundamental step is to fully and faithfully implement the important consensus reached by both leaders, it said.
From China's point of view, the Taiwan issue was expected to figure prominently in the talks.
Last week, China's Foreign Minister Wang told US Secretary of State Marco Rubio, during their telephone talks, that the US should make the right choice about the self-ruled Taiwan.
China claims Taiwan as part of its own and has been ramping up military pressure on the island with periodic military drills around the island.
VIDEO | Beijing: US President Donald Trump arrives in China for high stakes meeting with Chinese President Xi Jinping.
— Press Trust of India (@PTI_News) May 13, 2026
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