No T-cell left behind, an explanation to why we sleep and more in my picks of the week from RB

Another week has gone by and some very interesting molbio blog posts have been aggregated into Researchblogging.org. Every week [see my opening post on the matter], I'll select some blog posts I consider particularly interesting in the field of molecular biology [see here to get a sense of the criteria that will be used], briefly describe them and list them here for you to check out.

Note that I'm only taking into consideration the molbio-related blog posts aggregated under "Biology".

Three blog posts were selected this week:

1) The diversity of antigen receptors expressed by T-cells is enormous. The amount, then, of T-cells expressing a specific receptor for a particular antigen is very low (apparently less than 1 in 10⁵ cells). The vast expansion of specific T-cells we see a few days after an infection is the result of two processes: 1) Clonal selection, which refers to the recognition of this particular antigen by a specific (and small) subset of naïve T-cells and 2) Clonal expansion, which refers to a massive expansion of these selected clones after recognition, which gives rise to a population large enough to try to fight the pathogen. A question arises, then: when we do see clonal expansion, does this result from the recognition of the antigen by all the T-cells specific for the presented antigen, or only from a small subset of these that randomly (and luckily) interacted with the presenting cell?

Ian York (a regularly highlighted blogger in my picks of the week) discusses a recent article reporting that apparently clonal selection is extremely efficient and almost all the T-cells that potentially can recognize the particular antigen, do and expand.

2) Despite the vast amount of evidence behind AIDS research, there are still some groups denying the fact that HIV is the causative agent of AIDS.
Ben Vincent presents his ideas regarding the effects this “denialism” can have on the population and discusses “trust” in science.

3) This next blog post piqued my interest as my research focuses on circadian biology. Why do we sleep? Does it play a restorative function? Neuroskeptic discusses a recent review article proposing an alternative idea: that the evolutionary function of sleep is simply to ensure that animals are only active when the benefits of movement outweigh its costs and not because it’s physiologically needed. In other words, you’ll be active only when it’s useful for you to be active. Be sure to check the comments section for provocative discussions!

That's it for this week. Stay tuned for more MolBio Research Highlights!

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Some of the articles discussed in this week's selected posts:

van Heijst, J., Gerlach, C., Swart, E., Sie, D., Nunes-Alves, C., Kerkhoven, R., Arens, R., Correia-Neves, M., Schepers, K., & Schumacher, T. (2009). Recruitment of Antigen-Specific CD8+ T Cells in Response to Infection Is Markedly Efficient Science, 325 (5945), 1265-1269 DOI: 10.1126/science.1175455

Ascher, M., Sheppard, H., Jr, W., & Vittinghoff, E. (1993). Does drug use cause AIDS? Nature, 362 (6416), 103-104 DOI: 10.1038/362103a0

Nattrass, N. (2008). AIDS and the Scientific Governance of Medicine in Post-Apartheid South Africa African Affairs, 107 (427), 157-176 DOI: 10.1093/afraf/adm087

Siegel, J. (2009). Sleep viewed as a state of adaptive inactivity Nature Reviews Neuroscience, 10 (10), 747-753 DOI: 10.1038/nrn2697