In brief (October 2014): immunology, sea levels, gender stereotype, and nanomedicine

A selection from what I’ve read over the past couple of months:
immune response and genetic variation, or how interindividual genetic variation affects immune cell behavior, contributing to differences in how people respond to pathogens and how susceptible they are to develop autoimmune diseases,
ice melting and sea rising, or how global seal levels and ice volumes have changed over the past 35,000 years,
gender and speaking up, or how stereotypes related to gender affect an individual’s decision to contribute his/her ideas to a group,
anticancer nanomedicine, or how nano should nanoparticles be to optimally penetrate tumor tissue and exert their anticancer effect.

  • Immune response and genetic variation

The immune system must walk a fine line between mounting effective responses to defend the organism from invading pathogens and limiting the extent of collateral damage that may result from uncontrolled responses. The activation of a type of immune cells called T cells is central to the adaptive arm of the immune response: it is achieved when a piece of the invader (antigen) is mounted onto a molecule called major histocompatibility complex (MHC) and presented to T cells in presence of other “danger” signals; the T cell that possesses a receptor matching the antigen then becomes activated, starting an immune response that will be specific for the particular pathogen present.

There is a broad diversity of MHC molecules among humans, making individuals vary in their ability to present different antigens efficiently. This underlies in part why some people will get rid of an infection more easily than others, but also why some people are more likely to develop an autoimmune disease. Little is known, however, on how genetic variation affects the other end of the antigen presentation-T cell activation process, that is, how the T cell responds. In a study involving 348 individuals with Asian, African, or European ancestry, researchers analyzed how T cells isolated from donors’ blood responded to antigenic stimulation and found that, while there was a consistent pattern across individuals, there were also interindividual differences in the level of expression (production) of certain molecules, reflecting differences in T cell activation. The variation was most important in the expression of cytokines, molecules that function as mediators to orchestrate and coordinate the immune response. The researchers identified genetic variations associated with a particular type of regulation (cis) of gene expression and estimated that these accounted for about 25% of the interindividual variation observed in the T cell response, the rest being likely due to environmental factors, individual immunological history, or other types of genetic regulation. The researchers went on to identify a particular genetic variation affecting the expression of the IL2RA gene, which is known to be associated with autoimmune disease such as multiple sclerosis and type 1 diabetes.

(Ye et al. Science 12 September 2014. doi: 10.1126/science.1254665)

  • Ice melting and sea rising

A study published in PNAS in September presents a new analysis of sea level and global ice volume on Earth over a time period spanning the last 35,000 years. The researchers used different sea-level indicators (such as fossil coral, fossil terrestrial plants, etc.) from many different locations away from the former ice margins to estimate the variation of ice and ocean volume from the onset of the Last Glacial Maximum (about 35,000 years ago) to the present day. They reported, in chronological order: a slow fall in sea level from 35,000 to 31, 000 years ago followed by a more rapid fall between 31,000-29,000 years ago, indicating a period of rapid ice growth marking the onset of peak glaciation; constant or slowly increasing ice volumes between 29,000 and 21,000 years ago; onset of deglaciation about 20,000 years ago, which continued until about 7,000 years ago (during that period, the researchers found there were times of rapid sea level rise as well as periods of near-constant or slowly rising sea levels); progressively decreasing rates of sea level rise from about 6,700 years ago to recent time, with a total global rise of about 4m within that period, of which about 3m happened between 6,700 and 4,200 years ago, and less than 1m further occurred from 4,200 years ago to about 150-100 years ago.

Importantly, the researchers highlight the fact that over the past 4,000 years (until 150-100 years ago), there is no evidence of global sea level varying by more than 15-20cm on time scales of about 200 years. Which makes the recent sea level rise of about 20cm since the start of the 20th century stand out.

(Lambeck et al. PNAS 13 October 2014. doi: 10.1073/pnas.1411762111)

  • Gender and speaking up

Even when an individual is knowledgeable in a given area, how much he/she will contribute ideas to a group discussion within that area is influenced by the gender stereotype associated with that particular domain. A study found that men and women were less willing to contribute ideas in areas that were stereotypically outside of their gender’s domain (for example sports for women, arts for men). As a result, it may be difficult to identify who in a group may be the most talented and knowledgeable members, and the global group performance is affected. The author also reports that, although both men and women are likely to have a missed opportunity (not contributing a correct answer to the question asked) in a female-typed (for men) or male-typed (for women) domain, the effect is more pronounced for women than for men.

(Coffman KB, The Quarterly Journal of Economics 12 September 2014. doi: 10.1093/qje/qju023 ; full text available here)

  • Anticancer nanomedicine

Nanomedicine deals with particles at the nanometer scale (a nanometer is a millionth of a millimeter; to put it another way, a nanometer is to a millimeter what a millimeter is to a kilometer). In a study published in PNAS, researchers evaluated the biological profiles of nanoparticles of different sizes (20, 50, and 200 nanometers) to find what the optimal size would be for anticancer drug delivery. Their data indicate that the 50-nanometer particles had the best profile when taking into account tumor tissue penetration, internalization by the cancer cells and tumor clearance.

(Tang et al. PNAS 14 October 2014. doi: 10.1073/pnas.1411499111)


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