Modeling of immune life history and body growth: the role of antigen burden

In this paper, a recently developed mathematical model of age related changes in population of peripheral T cells (Romanyukha, Yashin, 2003) is used to describe ontogenetic changes of the immune system. The treatise is based on the assumption of linear dependence of antigen load from basal metabolic rate, which, in turn, depends on body mass following the allometric relationship – 3/4 power scaling law (Kleiber, 1932; West, Brown, 2005). Energy cost of antigen burden, i.e. the energy needed to produce and maintain immune cells plus the energy loss due to infectious diseases, is estimated and used as a measure of the immune system effectiveness. The dependence of optimal resource allocation from the parameters of antigen load is studied.

Modeling of Immunosenescence and Risk of Death from Respiratory Infections: Evaluation of the Role of Antigenic Load and Population Heterogeneity

It is well known that efficacy of immune functions declines with age. It results in an increase of severity and duration of respiratory infections and also in dramatic growth of risk of death due to these diseases after age 65. The goal of this work is to describe and investigate the mechanism underlying the age pattern of the mortality rate caused by infectious diseases and to determine the cause-specific hazard rate as a function of immune system characteristics. For these purposes we develop a three-compartment model explaining observed risk-of-death. The model incorporates up-to-date knowledge about cellular mechanisms of aging, disease dynamics, population heterogeneity in resistance to infections, and intrinsic aging rate. The results of modeling show that the age-trajectory of mortality caused by respiratory infections may be explained by the value of antigenic load, frequency of infections and the rate of aging of the stem cell population (i.e. the population of T-lymphocyte progenitor cells). The deceleration of infection-induced mortality at advanced age can be explained by selection of individuals with a slower rate of stem cell aging. Parameter estimates derived from fitting mortality data indicate that infection burden was monotonically decreasing during the twentieth century, and changes in total antigenic load were gender-specific: it experienced periodic fluctuations in males and increased approximately two-fold in females

Electron paramagnetic resonance (EPR) in medical dosimetry

This paper describes the fundamentals of electron paramagnetic resonance (EPR) and its application to retrospective measurements of clinically significant doses of ionizing radiation. X-band is the most widely used in EPR dosimetry because it represents a good compromise between sensitivity, sample size and water content in the sample. Higher frequency bands (e.g., W and Q) provide higher sensitivity, but they are also greatly influenced by water content. L and S bands can be used for EPR measurements in samples with high water content but they are less sensitive than X-band. Quality control for therapeutic radiation facilities using X-band EPR spectrometry of alanine is also presented

Retrospective and real-time semiconductor dosimetry: applications to geological dating and brachytherapy quality assurance

In this thesis solid state semiconductor dosimetry is applied to the improvement of luminescence dating techniques (part 1) and quality assurance in high dose rate (HDR) brachytherapy (BT) cancer treatments (part 2). The aim of part 1 is the development, testing, and application of a novel method to measure spatially resolved dose rates in sediment samples using the Timepix pixelated detector. The Timepix contains an array of 256x256 pixels, each 55x55 μm in size and with its own preamplifier, discriminator and digital counter, and is able to provide the position and pixel-by-pixel count rate of the incident radiation. The development of a method to measure sediment samples and derive spatially resolved dose rates is described, followed by its application to sediment samples from Liang Bua and Denisova Cave archeological sites

EPR measurements of fingernails in Q-band

Results of a feasibility study for the use of the Q-band EPR measurements of fingernails are presented. Details of the first protocol developed for Q-band (34 GHz) EPR dose measurements in fingernails and preliminary results of a dosimetry study in comparison with the commonly-used X-band (9 GHz) are reported. It was found that 1-5 mg sample mass was sufficient for EPR measurements in fingernails in the Q-band, which is significantly less than the 15-30 mg needed for the X-band. This finding makes it possible to obtain sufficient fingernail sample for dose measurements, practically from every finger of any person. Another finding was that the spectral resolution of the mechanically-induced signal (MIS) and radiation-induced signal (RIS) in the Q-band was significantly better than in the X-band. The RIS and MIS in the Q-band spectrum have a more complex structure than in the X-band, which potentially offers the possibility to do dose measurements in fingernails without treatment and immediately after clipping. These findings and recent results related to fingernail dosimetry in the Q-band and its perspectives are discussed here

Energy cost of infection burden: An approach to understanding the dynamics of host-pathogen interactions

Abstract A mathematical model of long-term immune defense against infection was used to estimate the energy involved in the principal processes of immune resistance during periods of health and infection. From these values, an optimal level of energy was determined for immune response depending on infection burden. The present findings suggest that weak but prevalent pathogens lead to latent or chronic infection, whereas more virulent but less prevalent pathogens result in acute infection. This energy-based approach offers insight into the mechanisms of immune system adaptation leading to the development of chronic infectious diseases and immune deficiencies. Published by Elsevier Ltd