An investigation into the interaction between hippocampal cells and lymphocytes and its influence on hippocampal network activity

Student thesis: Doctoral Thesis

Abstract

While the brain is no longer recognized as an immune-privileged site, the role of infiltrating T cells in either homeostasis, protective or pathological conditions is still poorly understood. In the present study, I hypothesize that neuronal-lymphocyte interactions lead to altered hippocampal network activity. Therefore, I aim to investigate contact-dependent and -independent effect(s) of lymphocytes on neuronal and astrocytic activity and synaptic communication. Mouse primary hippocampal cultures were prepared on coverslips and in microfluidic devices. Standard Ca2+ imaging techniques were used to monitor cellular excitability following treatment (1 hour) with naïve lymphocytes, lymphocyte conditioned medium (LCM) or recombinant IL-16 (rIL-16; 300 pg mL-1 ). ELISAs confirmed IL-16 in LCM. LCM but not lymphocyte exposure significantly impaired glutamate-induced increases in neuronal intracellular calcium (n[Ca2+]i) compared to HCM control but both were without effect on KCl-induced elevations in n[Ca2+]i and ADP- and glutamate-induced astrocytic [Ca2+]i (a[Ca2+]i) responses. IL-16 levels were elevated in LCM but not during lymphocyte exposure, which indicates that IL-16 is likely to underlie the observed effects with LCM. Interestingly, data has shown a trend towards rIL-16-mediated (300 pg mL-1 ) impaired glutamate-induced n[Ca2+]i increases and was without effect on KCl-induced n[Ca2+]i increases and ADP- and glutamate-induced a[Ca2+]i responses. As mouse hippocampal neurons and astrocytes do not express CD4 the possible effects observed with LCM and IL-16 treatment were considered CD4-independent. Furthermore, my data showsfunctional glutamate-induced neuronal synaptic communication between two mouse networks cultured in microfluidic devices. However, contact-dependent lymphocyte effects on glutamate-induced n[Ca2+]i increases and synaptic communication could not be confirmed in these microfluidic devices. It was shown that lymphocytes do not inducelymphocyte-mediated hippocampal cytotoxicity. VI In conclusion, presented data shows that lymphocytes do not mediate hippocampal cytotoxicity and that their soluble mediators, likely to be IL-16, impair hippocampal Ca2+ signalling via glutamate receptor modulation.
Date of Award1 Oct 2018
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorTrevor Bushell (Supervisor) & Hui-Rong Jiang (Supervisor)

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