B- and T-lymphocyte subset numbers in the migrating lymphocyte pool of the rat: the influence of interferon-gamma on its mobilization monitored through blood and lymph

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

An application of linear output error modelling for studying lymphocyte migration in peripheral lymphoid tissues

Lymphocyte recirculation between lymphatic and blood vessels and migration through tissues are essential mechanisms underlying immunological surveillance. However, the kinetics of lymphocyte migration through lymphoid tissues remains poorly understood. The present study of lymphocyte migration, based on a sheep model and entailing the long term cannulation of blood vessels and lymphatic vessels efferent from lymph nodes, represents the first attempt to apply control engineering based models to overcome some of the experimental impediments to understanding the complex phenomena involved in lymphocyte migration. An output error model order (1,2,nk) was systematically selected under given criteria from four classes of Linear Time-Invariant Single-Input Single-Output, (LTI-SISO) systems to represent the peripheral lymph node system. The unit impulse responses were simulated under noise free conditions and their features were extracted to describe the dynamics of the system. The findings from this study revealed novel information about several aspects of the dynamics of lymphocyte migration.

Modelling of peripheral lymphocyte migration: system identification approach

This is the first application of the prediction error method (PEM) of system identification to modelling lymphocyte migration through peripheral lymphoid tissue. The PEM was applied to the emergence of labelled lymphocytes from the efferent lymphatic of a lymph node following their intravenous administration. Advantages of PEM included the capacity to calculate the response to a unit impulse stimulus, unavailable to direct observation, and to allow for the return to the node of labelled cells that had already recirculated once. Calculation of the system delay (time between introduction of cells into the blood and their first appearance in lymph) indicated 4.67 +/- 1.05 h for the total lymphocyte population. The peak in efferent lymph occurred at 11.91 +/- 4.68 h, much earlier than previous reports, which were affected by cells that had already recirculated. While 75% of labelled cells had emerged in efferent lymph by 20.77 +/- 5.62 h, 86.38 +/- 29.44 h was required for 100% emergence. The considerable heterogeneity in migratory behaviour is likely to reflect frequency and duration of binding of lymphocytes by dendritic cells in paracortical cord corridors. It is proposed that differences in the speed with which lymphocytes pass along corridors depend on their functional status, in particular whether they are naïve or memory cells.

The simulation of density-dependent effects in the recirculation of T lymphocytes

T-lymphocyte recirculation appears to be slower in nude or irradiated rats as compared with normal rats. A mathematical model of T-lymphocyte recirculation that incorporates interactions between T cells and dendritic cells in the lymphoid tissue is presented. It is shown that these interactions are able to explain the differences in recirculation times between normal and nude or irradiated rats, and also the time-scales seen in long-term thoracic duct cannulations.

The neuropeptide substance P does not influence the migration of B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes from blood to lymph in the normal rat

Thoracic duct lymphocytes (TDL) continuously patrol through the body, facilitating immune responses at most sites. The neuropeptide Substance P might regulate immune responses by influencing the migration of TDL. Therefore, it was investigated whether Substance P affects the migration of thoracic duct B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes from blood to lymph in vivo. Labelled TDL were either incubated with Substance P and then injected into normal rats, or incubated without Substance P and then injected into rats continuously receiving Substance P intravenously. The numbers of labeled B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes were determined in blood and thoracic duct lymph for 1 and 5 days, respectively. Neither the in vitro incubation with Substance P nor its in vivo application influenced the disappearance of any lymphocyte subset from the blood or its reappearance in the lymph. In addition, continuous intravenous application of the Substance P antagonist CP 96.345 did not alter the volume or the lymphocyte number of the efferent lymph. The present study indicates that the nervous system does not influence immune responses via Substance P by altering the migration pattern of B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes.

Acute and chronic experimental Trypanosoma cruzi infection in the rat. Response to systemic treatment with recombinant rat interferon-gamma

We examined the effects of recombinant rat interferon-gamma (IFN-gamma) injections on the parasitologic, serologic, immunologic and histopathologic features of acute and chronic experimental Trypanosoma cruzi (T. cruzi) infections in "l" rats. Upon infection at weaning, two rat groups were allocated to receive a 20-day cycle of IFN-gamma injections, 20,000 IU/rat each, which started at 1, and 7 days post-infection (pi). Treatment with IFN-gamma, initiated at either 1 or 7 days pi, resulted in comparatively lower peak parasitemias (P < 0.02) but in similar levels of anti-T. cruzi circulating antibodies and serum IFN-gamma activities. The latter appeared significantly increased during acute infection whereas biologically active tumor necrosis factor was virtually undetectable in serum from infected rats regardless of whether they had been given IFN-gamma or not. The prevalence of chronic focal myocarditis in IFN-gamma-treated infected rats showed no differences with respect to the one recorded in control-infected counterparts. The inverse CD4/CD8 ratio of spleen and lymph node T cells that usually accompanies chronic infection was reversed by IFN-gamma. Mononuclear cells carrying class II I-A and I-E molecules, that were found to have increased at both compartments, appeared also modified upon IFN-gamma treatment with an overincrease of I-A-positive cells, and a normalization of I-E-bearing cells.