Just wondering can antibiotics kill human cells (one that are broad spectrum that target plasma membrane)?? Also about immunity sac- are wi born with every possible antibody to fight against every possible antigen that could appear?? Or what happens if our body does not have the antibody specific to an antigen (can that happen)?? Also hen cytotoxic T cells bind to antigen of virus infected cell/ cancer cell etc. how do the cytotoxic T cell detect the antigen on MHC 1 marker if the cell is already virus infected or cancer cell or transplanted tissue?? Also do do cytotoxic T cells also kill larger organisms such as worms and eukaryotic organisms or what kills it when invades the body? Thanks
1. Antibiotics would not normally kill human cells because even when they target something relatively 'ubiquitous' eg plasma membranes, they focus on targeting the parts that are specific to the bacteria. The plasma membranes of bacteria and eukaryotes are subtly different. Most antibiotics target bacteria-specific systems for protein synthesis or nucleic acid synthesis. Some with more severe side effects may damage human cells, especially when administered for a long time, but they usually have a clear preference for bacterial cells. Antimicrobials used against fungal infections are far less selectively toxic and are more likely to harm human cells - this is because the target and the host are both eukaryotic.
2. Your body continues to produce B cells throughout its life (so you're not born with every B cell per se, in fact you're not born with a great immune system at all which is why you need antibodies to be transmitted from your mother in the womb to protect you for the first few months of life), which are the cells that produce antibodies. Typically, multiple cells would be capable of recognising a single antigen. With this kind of overlap and the fact that B cells are continuously produced it is unlikely that you would lack an antibody specific for an entire microbe. You may lack antibodies specific to some antigens but the fact that microbes are made up of a multitude of antigens means you are 'covered' overall and you won't end up dying. Even if there were a hypothetical scenario where you lacked all of the possible B cells to recognise a certain antigen you might still not die because you would have T cell responses that could contribute to coordinating an immune cell against it.
3. I'm not sure I understand your question entirely but I'll try to answer anyway. When the cell becomes infected or cancerous it will start processing and expressing the non-self proteins on MHC-I molecules. The T cell can recognise these as long as the infected/cancerous cell continues to express MHC-I.
4. The cytotoxic T cell cannot kill the worms or eukaryotic cells directly using cytotoxic molecules because these organisms wouldn't be expressing MHC-I so the T cell can't recognise them as foreign. Cytotoxic T cells can help clear some parasitic infections (eg malaria) when the parasites are intracellular, allowing a human cell an opportunity to express the foreign antigen on MHC-I. In this case the cytotoxic T cell would kill the infected cell harbouring the eukaryotic parasite. For worms, T cells still play a role but it's usually helper T cells that secrete cytokines and coordinate the immune response that would help this sort of infection to be cleared (in addition to B cells).
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