BOTH Immune System to Viral/ Bacterial Infection

[persona_grata]

I have a question about the immune response to a pathogen, specifically the difference in responses between viral and bacterial infections, I am really lost, so I would greatly appreciate if you could break it down into steps and correct me if needed!

You know when we're talking about the whole non-specific innate immunity, is it the same for both viruses and bacteria cells? Are they both phagocytosed by neutrophils and macrophages? Also, does haptoglobin prevent viruses from having an access to iron in haemoglobin too?

And now also the specific immune system, specifically in terms of the bacterial infection. What I don't get is this: since bacteria are considered to be an exogenous pathogen, does it mean that it cannot be targeted by killer T-cells (CTLs) because this pathway is never initiated? Because the specific immune system pathway of bacterial infection stops with the production of plasma cells and memory cells? Does it mean that the only way of killing bacteria is by disabling them with antibodies and then slowly phagocytosing them?


And now in terms of adaptive immune system and a viral infection: so, how I understand it is that...

• APC captures a virus and breaks it down into peptides and then expresses in using the MHC-II molecule (for CD4+) and MHC-I molecule (for CD8+).
  
• It then migrates into the lymph nodes where it tries to find a matching CD4+ cell.
  
• At the same time, matching naïve CD8+ cells attach to the MHC-1 complex of an APC.
  
• Eventually, CD4+ and CD8+ cells connect to APCs and CD4+ cells release IL-2 which activates CD8+ cells (makes them cytotoxic) and causes them to proliferate.
• And then after a few steps, it ends up with cytotoxic T-cells causing apoptosis of infected cells. Most of the cytotoxic T-cells are then destroyed but some are left in our body and they're called memory T-cells.

But the process doesn't always have to start with the initiation of CD8+ cells using APCs, it is still possible to initiate this process if a naïve T-cell finds a cell that has been infected somewhere in the body? But then how does this process continue, does it involve T-helper cells and the proliferation of cytotoxic T-cells with the similar antigen peptide molecule. Also, how does this process produce antibodies, because it does seem like most of the time it ends up with cell apoptosis.

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