2.60 Describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen

What are white blood cells?
They are specialized cells that protect your body from pathogens (which can be harmful and cause disease)

I accidentally explained this in a previous post but I'll do so again:

Phagocytes
These types of white blood cells detect pathogens through a chemical trail that they leave behind. Their cytoplasm forms feelers called pseudopodia  which engulf the pathogen and forms a vacuole. The phagocyte releases digestive enzymes into the vacuole which then kill / digest it (the pathogen)

This process is called phagocytosis.

Figure 1

Lymphocytes
These white blood cells stand back a bit compared to the phagocytes (don't say that in an exam, for the love of elves, don't!). They release antibodies which are specific / complimentary to the antigens on the surface of the pathogen (also how it recognizes it). There are various types of lymphocytes - some cause the pathogens to stick together so phagocytes can engulf them all (the string of pathogens, I mean) , others disable / neutralize the cell and others latch onto the pathogen to attract phagocytes. When a lymphocyte encounters a pathogen and produces an antibody specific to that pathogen, it splits - one of the cells becomes a memory cell (See how vaccination works) and the other releases antibodies.

Click here for image

(because for some reason when I tried to put an image in, it didn't work)

Basic points on memory cells

• Memory cells created when lymphocyte splits
• Allows immune system to "remember" the disease (do not say that in an exam!!)
• Upon re-infection, immune response is faster (secondary immune response is faster)
• When the organism is re-infected, antibodies are produced much much quicker

:)

Lymphocyte types summary

• Some cause pathogens to stick together (so phagocytes engulf them all)
• Some latch onto them to attract phagocytes
• Some neutralize the cell (or disable it, same thing)

Some also make pathogens explode but I'm not sure about that one so better not mention that in an assessment, be it an exam or just a test. Basically, do not mention that in an exam unless you have researched further and know how it works.

Little extra from Annabel: Just write all four things in an exam, even if it is a 3 mark question because you never know with the mark scheme... :)