Basic science for the clinician 32: T-cells with regulatory function

Neuroimmune Interaction in the Regulation of Peripheral Opioid-Mediated Analgesia in Inflammation

Peripheral immune cell-mediated analgesia in inflammation is an important endogenous mechanism of pain control. Opioid receptors localized on peripheral sensory nerve terminals are activated by endogenous opioid peptides released from immune cells to produce significant analgesia. Following transendothelial migration of opioid-containing leukocytes into peripheral sites of inflammation, opioid peptides are released into a harsh milieu associated with an increase in temperature, low pH, and high proteolytic activity. Together, this microenvironment has been suggested to increase the activity of opioid peptide metabolism. Therefore, the proximity of immune cells and nerve fibers may be essential to produce adequate analgesic effects. Close associations between opioid-containing immune cells and peripheral nerve terminals have been observed. However, it is not yet determined whether these immune cells actually form synaptic-like contacts with peripheral sensory terminals and/or whether they secrete opioids in a paracrine manner. This review will provide novel insight into the peripheral mechanisms of immune-derived analgesia in inflammation, in particular, the importance of direct interactions between immune cells and the peripheral nervous system.

Basic science for the clinician 45: CD4+ T-cell subsets of probable clinical consequence

I have often said "blessed be the splitters, for they shall inherit the earth." By that I mean that it is only by studying carefully culled populations, approaching, but never quite reaching, homogeneity that we can ever gain real insights into rheumatologic diseases. Differentiating tuberculous from gouty from rheumatoid arthritis was a good start, and when Moll and Wright identified the seronegative spondyloarthropathies, we were on our way to establishing "splitters" as leaders. Predictably, once T cells were identified as different from B cells, the floodgates opened. Subsets galore were described, with more isolated populations in the T-cell family, but we are now finding heterogeneity in B-cell populations, as well, which has been discussed in a previous article in this series. But as for T cells... well, it has not been smooth sailing. I initially trained in a laboratory that was firmly committed to the proposition that there were within the CD8 population not only cytotoxic cells but also "suppressor cells." Problem is, no one could ever isolate the little buggers, and so the idea of a suppressor or regulatory subpopulation of CD8+ T cells went the way of the Edsel. As noted in a previous article in this series, T regulatory cells were finally identified but not within the CD8+ population. And there are other regulatory subsets within both CD4+ and CD8+ T-cells populations and even new effector and memory populations that can be identified by their surface markers and functions. It is high time to review some of them; some of these populations may be involved in the immunopathogenesis of our diseases and undoubtedly will shortly be targets of immunotherapeutics. Although previous articles in this series discussed some of these subsets, I thought expanding on what is known about another recently described subset and putting them all together in one review might be helpful.

Basic science for the clinician 38: B cells, factories, and immunomodulators

In a previous article in this series, we explored how developing pre-T cells learn how to be well-behaved T cells that recognize and honor the "self versus nonself" dichotomy of the universe. B cells do much of the same sort of thing, with multipotent stem cells becoming committed to ultimately becoming B cells within the bone marrow and then, after judicious culling of the flock, going off to the spleen to learn the final lessons needed to become "well-behaved" B cells. Like with T cells, there are a large number of things that can, and do, go wrong. If there is a failure of the system and B cells do not develop properly, hypogammaglobulinemia may develop as a result of a number of immune deficiency syndromes that can be quite devastating. If autoreactive cells survive to emerge into the periphery, autoimmunity, either organ-specific or more global, may occur. If B cells in the periphery proliferate in an uncontrolled fashion, a variety of B cell lymphoproliferative syndromes may develop, recognizable by the phenotypic markers of their originating B cell lineage level of differentiation. The full details of how autoreactive B cells survive and thrive, only to cause disease, are not yet clear, but identification of many of the phenotypic surface markers and circulating growth factors identified to this point have borne therapeutic fruit.