With modern plumbing and hygiene, the number of nasty microbes we humans are exposed to has plummeted, while the rate of autoimmune diseases and allergies has shot up. Are those related? Proponents of the hygiene hypothesis think so: our immune system is supposed to develop by encountering microbes, so being too clean throws it out of whack as the immune system overreacts to minor insults.
A new study found that mice raised germ-free had especially high numbers of invariant natural killer T cells (iNKT) in their colons and lungs—the mouse versions of inflammatory bowel disease and asthma, respectively. Most evidence supporting the hygiene hypothesis has just been in observed correlations, so this research that identifies a plausible molecular mechanism is good evidence for how over-cleanliness might cause immune dysfunction.
Fruit fly larvae and wasp
What’s the News: Fruit fly larvae have unusually high alcohol tolerance, which scientists used to think was because they happen to feed on yeast in rotting fruit. Turns out they’re in it for the alcohol, too—as medication. According to a new study*, alcohol protects them from the wasp parasites that lay eggs in fruit fly larvae.
Takin’ one for the team.
What’s the News: Clearly, as anyone suffering through a cold right now can tell you, our immune systems aren’t all they could be when it comes to keeping us disease-free. And what’s worse, the same viruses that have some people hawking up phlegm for weeks can give their roommates or spouses no more than a brief sniffle, hammering home the fact that the immune system wealth isn’t distributed evenly. Why hasn’t evolution dealt with this problem already and given us all impenetrable defenses?
As it turns out, it’s not just that evolution takes its own sweet time. It’s also that a species benefits from having individuals be immune to some things and vulnerable to others, a new study shows.
Booze inhibits more than just your judgement: it impairs your immune system’s ability to fight off pathogens, according to a study published last week in the journal BMC Immunology. Researchers exposed human monocytes, a type of white blood cell vital for a functioning immune system, to an amount of alcohol equivalent to a blood alcohol concentration of 0.1 (around the legal level in most states). Compared to booze-free cells, monocytes exposed to both short- and long-term levels of alcohol produced significantly less type 1 interferons, chemicals the help recruit immune cells to stage an antiviral response (and also have anti-tumor activity). Excessive drinking has long been thought to interfere with the body’s ability to fight disease, and boozing is an important risk factor for hepatitis C and barrier to treatment in HIV. But not much had been known about the mechanisms behind the effect.
Scientists have now sequenced the genome of the Atlantic cod, revealing something unusual: the cod is missing an important component of the adaptive immune system found in almost all jawed vertebrates. In particular, when the researchers compared the cod’s genome to that of the stickleback (a closely related fish that has already been sequenced), they saw that the Atlantic cod does not have genes that code for the proteins MHC II, CD4, and invariant chain, all of which work together to help the body recognize and fight off invading bacteria and parasites.
Could Neanderthal DNA have protected our ancestors from diseases?
What’s the News: While we humans have certainly outlasted our hominin cousins, new research shows that Neanderthal and Denisovan genes may have helped us spread far and wide. By mating with the two species, our ancestors acquired genes that allowed them to adapt to diseases outside of Africa far quicker than would have been otherwise possible, according to Peter Parham, a professor of microbiology and immunology at Stanford University.
Mouse embyronic stem cells
What’s the News: Reprogrammed stem cells—cells taken from an adult and turned back into stem cells—can be rejected by the body, at least in mice, suggests a new Nature study. Donated tissues and organs are often attacked by a patient’s immune system, since reprogrammed stem cells can be made from a patient’s own skin, researchers had hoped these cells offered a way to avoid such rejection by letting patients, in essence, donate tissue to themselves. But the new finding may be a significant setback to what is a promising line of treatment.
Metastatic melanoma cells
What’s the News: Souped-up cells from a patient’s own immune system could one day be used to treat advanced melanoma, according to a preliminary study published in Science Translational Medicine investigating the safety of the technique. The researchers manipulated a patient’s immune system cells to better recognize cancer cells in the lab and then re-introduced those cells into the body—an approach called “adoptive T-cell therapy.”
Earlier this week at a scientific conference in Boston, HIV researchers announced a remarkable success in countering the virus’ drain on the immune system. But this early step is far from a cure.
Why it’s exciting:
Carl June and colleagues tested six male patients who already had HIV and were taking a standard antiviral regimen. Like many HIV patients, the drugs helped them, but their counts of immune cells stayed low. June’s team tested a therapy created by Sangamo BioSciences in Richmond, California, that alters a patient’s actual white blood cells to make them more HIV-resistant.
Researchers removed a sample of CD4+ T cells, the type of immune cells affected by HIV, from each man and used Sangamo’s enzyme to disrupt the CCR5 gene, which encodes a protein that HIV uses to enter CD4+ cells. The engineered cells were then infused back into the patients. Immune-cell counts subsequently rose for five of the six patients who received the therapy. “It’s very exciting,” says John Rossi, a molecular biologist at the City of Hope’s Beckman Research Institute in Duarte, California. “If they did this several times in a given patient, you could establish a high percentage of resistant cells.” [Nature]
The idea came from the “Berlin Patient,” who we’ve written about before at 80beats. He became famous after receiving a donation of bone marrow from someone who carried a mutation in CCR5 that made them resistant to HIV.
Talk about early intervention. One day, a fetus with a genetic disease may be able to get treatment before it even leaves the womb–and that treatment will come in the form of an extra gift from mom. While this scenario will only come to pass if new mouse research can be translated to humans, the finding are exciting.
The new work solves a medical mystery. When researchers realized they could diagnose a fetus with certain genetic illnesses as early as the first trimester, they plunged into the search for in utero treatments. Ailments like sickle cell anemia and some immune disorders might be treatable with blood stem cells taken from a donor’s bone marrow, researchers thought: the transplanted cells would multiply and populate the fetus’s bone marrow with healthy blood-forming cells, and the fetus’s immature immune system wouldn’t reject the foreign entities. But when researchers tried such transplants, they didn’t work.
“The fact that fetal stem cell transplantation has not been very successful has been puzzling, especially given the widely accepted dogma that the immature fetal immune system can adapt to tolerate foreign substances,” said co-senior author Qizhi Tang…. “The surprising finding in our study is that the mother’s immune system is to blame.” [press release]