Hi everyone :)

As soons as pathogen aren't cleared from the innate system, the adaptive immune system is getting activated. It can be seperated into two ways of how it responds: humoral or cell-mediated. White blood cells, especially the lymphoctes play the major role. In the following article, I want to give you a little overview about this topic. In reality, the whole process is much more complex, as you can imagine, but as I have to learn it for my biology exam, for which the following is enough, I hope it is enough for you too, so enjoy ;)

How does it work?

graphic, showing the start of both immune answers

Cell-mediated

After the first contact with the anitgen, macrophages absorb the antigens through phagocytosis and disassemble them into their components. Then they present the foreign surface of the antigen on their MHC-2 protein. Resting T helper cells (T, because they mature in the thymus) get activated through the contact with the antigen represanting macrophages  and start to produce a hormone like substances called "cytokines"or "intereleukins". They enable the T helper cells to clone themself and to activate other cells such as the B lymphocytes (part of humoral answer).  The activation is a result of the CD-4 receptors of the T lymphoycte, which connect to the MHC-2 proteins on the dendrit/macrophage. T supressor and T memory cells are the resulting specified cells of the activation process. If the T lymphocte would have connected to the MHC-1 proteins with it's CD8 receptors, the T cell would have become a T killer cell or a T memory cell as well. The killer cell now destroys the infected cell trough lysis and the memory cells are able to expand to large numbers of effector T cells upon encountering their cognate antigen. The immune system now has "memory"  against previously encountered pathogens and can react faster, keeping the body immune. At the end, the supressor cells stop the whole process.

But wait... wasn't there something with the humoral responding? 

simple illustration, of the humoral and cell-mediated reaction

Humoral 

Humoral is the aspect of  immunity that is mediated by macromolecules found in extracellular fluids. 

Resting B-lymphoctes (B= maturing in the bone marrow) with fitting receptors recognise antigenes and get activated. To produce anitbodys, they get directly activated from an antigen or if they are naive cells, need the contact with a T helper cell (thats why the processes are connected). After having the contact with the T helper cell and the hormones, the start to clone and differ themselfs to plasmacells and B memory cells. The plasmacells are producing antibodys, immunglobolines and agglutinate the antigenes to an antibody-antigen-complex, which the body later gets rid of by phagocytosis from macrophages. The B memory cells have the same task as the the t memory cells: if the same antigen will ever be again in the body, a faster response will be the consequence, keeping the human body immune against the disease. The primary response (first contact with the antigen) is taking about 5-10 days and the secondary response (next contacts) will take 3-5 days and hold longer and also produce much more antibodys, as the memory cells were able to save the surface structures of the antigen, making the reaction faster.

Difference between primary and secondary immune response

The humoral reaction is finished, when the t supressor cell hempers the cytocines of the t helper cells

 -> the immune answer is finished

Conclusion

For me, it was good to revise the process before my exam and I hope you may learned something too. This article is just a very very small part of the complexity of the immune system and maybe you are interested in immune biology now. In the futute I can imagine, to give more detailed articles about this topic, because for me, it is incredible of what our body is capable of and how it works.

Have a nice day and check out some of my other posts, if you are interested in scientific content. :D

Source

Text

(translated) http://www.scheffel.og.bw.schule.de/faecher/science/biologie/immunologie/3immunantwort/immunant.htm

http://www.abcam.com/protocols/the-immune-system-and-the-antibody-response

https://en.wikipedia.org/wiki/Immune_system#Complement_system

Pictures 

https://textimgs.s3.amazonaws.com/boundless-biology/figure-17-03-05.jpe

http://weishendopublications.com/uploads/3/2/0/1/3201726/2353774_orig.jpg

https://image.slidesharecdn.com/immunitybyasogwainnocentkingsley1-131219110304-phpapp02/95/immunity-and-immune-system-by-asogwainnocentkingsley1-28-638.jpg?cb=1387452186