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T lymphocytes from the immune system are bone marrow-derived cells whose development and activities are carefully supervised by two sets of accessory cells. In the thymus, the immature young T lymphocytes are engulfed by epithelial “nurse cells” and retained in vacuoles, where most of them (95%) are negatively selected and removed when they have an incomplete development or express high affinity autoreactive receptors. The mature T lymphocytes that survive to this selection process leave the thymus and are controlled in the periphery by another subpopulation of accessory cells called “regulatory cells,” which reduce any excessive immune response and the risk of collateral injuries to healthy tissues. By different times and procedures, nurse cells and regulatory cells control both the development and the functions of T lymphocyte subpopulations. Disorders in the T lymphocytes development and migration have been observed in some parasitic diseases, which disrupt the thymic microenvironment of nurse cells. In other cases, parasites stimulate rather than depress the functions of regulatory T cells decreasing T-mediated host damages. This paper is a short review regarding some features of these accessory cells and their main interactions with T immature and mature lymphocytes. The modulatory role that neurotransmitters and hormones play in these interactions is also revised.

There is a huge generation of residual hydrocarbons resulting from the use of fossil fuels, which adversely affect organisms and ecosystems. The automotive wasted lubricating oil represents one of the most recalcitrant pollutants because its long persistence and slow degradation. That is why it is very important to carry out studies to assess the toxicity of this residue. In this work the response of two plant species, Vicia faba and Phaseolus coccineus, was evaluated during its growth in contamined soil with automotive wasted oil. The monitoring of temperature, pH and humidity of substrate was done along the growth process in both species. A higher percentage of germination was observed in seedlings of P. coccineus (78 %). The variables that determine toxicity in plants (height, stem thickness, root length, root volume and concentration of chlorophyll) show significant differences between soil contamined with wasted oil and the control soil (p ≤ 0.05). The correlation analysis showed that the most related variables were height-root length (R 2 = 0.74) and root length-root volume (R 2 = 0.85). The species that has greater tolerance to the hydrocarbon concentrations was P. coccineus. It was also possible to note that the prior treatment of composting in both soils is not sufficient to inhibit the toxicity of the wasted oil to grow V. faba and P. coccineus.

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