Hey all, I had a couple questions that surfaced whilst recapping immunity:
1. What are the roles of complement proteins in the inflammatory response? Do dendritic cells play any role?
- I read on Wikipedia that complement proteins attract macrophages and neutrophils, however, I thought cytokines released by the injured cells did this? Can someone please clarify? I also heard they promote inflammation but how does this work? Do they have any other roles?
2. How does the inflammatory response help the adaptive immune response occur?
I had the impression they were distinct as the inflammatory response does not retain immunological memory?
3. Why are antibodies relatively ineffective at fighting intracellular viral infections?
I can somewhat grasp this concept but am not too sure about it - are they ineffective on intracellular viral infections because they can only bind to foreign antigens and the invaded cell would only have its own normal MHC-I markers? But I thought these cells could display antigens of the pathogen on their MHC-I markers? Or is it because the cells cannot phagocytose the viruses and thus get the foreign antigens displayed?
4. Does clonal selection consist of BOTH the proliferation and differentiation of B and T-memory cells? Do T-memory cells work like B-memory cells as in they will differentiate into active cytotoxic-T cells if they encounter the same antigen presented on an MHC-I marker or active helper T-cells if they ____ (what circumstances would they diff. into active helper T-cells?)
Huge appreciation for whoever takes the time to answer as I'm aware this is a large influx of questions (whoops)
1. Complement proteins are involved in opsonisation, MAC deposition and chemotaxis (as far as VCE is concerned). Chemotaxis means chemical (chemo) attraction (taxis: to move in response to stimuli). Therefore, complement attracts immune cells to the site of infection in the inflammatory response. The release of cytokines by injured cells also acts to attract immune cells to the site of infection. Different substances can have the same function. The main role of dendritic cells is to engulf pathogenic agents and present these agents’ antigens to Tc cells.
2. The inflammatory response is a bridging mechanism between the innate and adaptive immune responses. Specific innate immune cells acquire antigenic fragments and present this to the adaptive immune response’s cells (i.e. Tc cells), this allows for the occurrence of the adaptive immune response.
3. Antibodies function extracellularly, causing; agglutination, opsonisation, neutralisation and complement activation. As viruses intracellularly attack cells, extracellular antibodies are inefficacious against them. (Note: Plasma B cells secrete antibodies into the bloodstream or lymph).
4. a) Clonal selection consists of neither proliferation or differentiation (hehe – how about that!?), it merely involves the binding of the epitope of an antigen to a specific receptor of a B cell, T cell etc. Clonal expansion, however involves proliferation.
b) B memory cells differentiate into B plasma cells or more B memory cells. T memory cells differentiate into T helper or T cytotoxic cells. In terms of conditions that are conducive to the differentiation of memory cells into specific cell types, I used to be familiar with the answer, however for now – I cannot seem to recall it. Hopefully someone else can help, though it is definitely outside of the study design.