Discovering How Cells Remember Infections Decades Later
Immunologists have long been perplexed by the question of exactly how immune cells remember an infection or a vaccination so that they can spring into action decades later. Research led by Professor Marc Hellerstein in the Department of Nutritional Sciences and Toxicology, in collaboration with investigators at Emory University, has found an answer: A small pool of the same immune cells that responded to the original invasion remain alive for years, developing unique features that keep them primed and waiting for the same microbe to reinvade the body.
Before this study, scientists knew that cells can remember an infection from up to 30 years earlier, but weren’t sure how. To tease apart this mystery, the research team tracked a specific kind of immune cell through the human body in the weeks, months, and years following a vaccination that gives long-term protection.
Using a technique that Hellerstein developed for his HIV/AIDS research in the 1990s that monitors the birth and death of cells in humans over long periods of time, the researchers tracked T cells inside people’s bodies after they were given the long-lasting yellow fever virus vaccine. They found that CD8+ T cells, responsible for long-term immunity against yellow fever, proliferate rapidly on exposure to the vaccine but then evolve, beginning about four weeks after the vaccination, into a “memory pool” of cells that live more than 10 times longer than the average T cell. Over time, the large pool shrinks to a small number of long-term memory cells, which are primed to provide late protection.
“This work addressed fundamental questions about the origin and longevity of human memory CD8+ T cells generated after an acute infection,” said Hellerstein, senior co-author of the study, which was published last December in the journal Nature. “Understanding the basis of effective long-term immune memory may help scientists develop better vaccines, understand differences among diseases, and diagnose the quality of an individual person’s immune responses.”
— Brett Israel
Palm Oil Plantations Fuel Pigs, Harm Forests
Increased demand for palm oil has caused widespread deforestation and biodiversity loss in Southeast Asia, and a new study by CNR researchers demonstrates that the impacts of expanding plantations of oil-producing palm trees are much worse than previously thought. Wildlife feeding on oil palm fruit can become overabundant and subsequently cause the chronic degradation of remaining nearby forests.
In a study lasting more than two decades, an international team of scientists observed immense shifts in tropical forests in Peninsular Malaysia. “We knew that forest understory was dying, but we didn’t understand why,” said Matthew Luskin, PhD ’16 Environmental Science, Policy, and Management (ESPM), lead author of the study. “Once we started looking outside the forest to the surrounding palm oil plantations, the story became clear.”
Oil palms produce fruit rich in an oil that can be found in a wide range of food and cosmetic products. Forest animals like monkeys and pigs also feed on the fruit, and with a proliferation of palm oil plantations their numbers can rapidly multiply.
In their study, published last December in the journal Nature Communications, the researchers found that the presence of oil palm fruit on such plantations led to a 100-fold increase in the number of wild boars living in the adjacent forests. In addition to eating tree fruits, wild boars have destructive behaviors such as rooting up soil for food and building nests, which can disrupt tree sapling density. By comparing such forests with forest areas that were fenced to exclude wild boars, the team found that wild boars reduced the number of small trees by over 50 percent, raising concerns about the future health of the forests.
“What’s most concerning about these findings is that the negative impacts of palm oil plantations are occurring deep within what otherwise looks like pristine forest—miles from the nearest plantation,” said ESPM professor Matthew D. Potts, a co-author of the study along with ESPM professor Justin Brashares.
Fresh Technology for Freshwater Research
Berkeley researchers are collaborating with the UC Natural Reserve System (NRS) to lead a new project that monitors changing freshwater resources across California. With a $2.2 million grant from the Gordon and Betty Moore Foundation, the California Heartbeat Initiative–Freshwater project will utilize drones and wireless sensor systems throughout the sites of the NRS, a network of protected lands covering more than 750,000 acres and representing many of the state’s habitat types. The goal of the program, said lead investigator and ESPM professor Todd Dawson, is “to deepen our understanding of how changes to climate and water are affecting natural and agricultural lands, and to predict how characteristics of these landscapes may shift in the future.” Other researchers involved in the project include David Ackerly, a professor in the Department of Integrative Biology, NRS director Peggy Fiedler, BS ’80, PhD ’85, Wildland Resource Science, and Maggi Kelly, an ESPM professor.