How Does The Immune System Work?

Brief Answer:
Innate immunity does not requires instructions

Detailed Answer:
Hello madam,

Thank you for asking an academic question at HCM.

I would like to give you information as follows:

1. There are basically two types of immunity: innate immunity and acquired immunity.

What you have described is all about acquired immunity. It has cells such as Lymphocytes (T-lympthocytes & B-lymphocytes), neutrophils & others.

2. T-lymphocytes are of many types - killer cells, helper cells and memory cells.

As the names suggest - helper cells give signals to other cells to kill or a cell or not.

Memory cells tells immune system to build a stronger immune response if an organism has already come contact with immune system in past.

Killer cells kill cells, but they need signals from other types of cells, especially helper cells.

B lymphocytes produce immunoglobulins (they are of 5 types) which are important for killing a microbe. Again, B lymphocytes need signals from T lymphocytes and others to produce antibodies.

So as long as one is talking about "acquired immunity", yes, it requires instructions and it works better if it has seen the pathogen before.

3. "Innate immunity" does not have such cells. It has its own cells, proteins & defense mechanisms which are quite different from those of acquired immunity.

I would like to mention some details of this immunity:

a. Its role is more or less of that of an initial protection. i.e., before lymphocytes and macrophages etc come into the picture

b. It works only against microbes. i.e., it cannot cause autoimmune disorders, cancers or allergies.

c. It is always present in all the healthy individuals.

d. It responds immediately. i.e., it does not have to wait for signals by other cells, recognition and memory etc,

4. Example of innate immunity are -

a. acid secretions in stomach - they kill so many pathogens and prevent them enter lower in the gastrointestinal tract.

b. There are some substances in tears, urine, saliva, respiratory and gastrointestinal secretions which can kill pathogens. They also expel pathogens.

c. Even pH is important against some organisms. e.g., vaginal pH is acidic due to some secretions which protect against some bacterias. If secretions are not proper or after menopause, the pH can change and a woman can get urine infections etc.

d. If talking about "cells", there are cells known as phagocytes, natural killer cells (NK cells) which are part of innate immune system. They directly identify what is called PAMS (pathogen-associated molecular patterns) in the bacteria and kill them directly without need for signals or inflammation.

e. Complement system, which is also a part of innate immunity, is a system of proteins, which directly recognizes some components of pathogens (including some viruses, bacteria, even cancer cells) and kills them by activation of complement cascade. There are 2 major pathways that this complement system can be activated - classical pathway and alternative pathway. This system also does not require signals from other cells as well as inflammation.

5. In fact, of course, our acquired immunity requires "training" and memory and so many things and it is very well developed in mammals.

It is the innate immunity that is present in us since birth and in fact it is the dominant system in plants, fungi, insects and primitive multi-cellular organisms for defense.

Hope above information will be useful to you.

Thank you & Regards,

Dr Parin N Parmar

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Brief Answer:
Agree, controversial role in carcinogenesis

Detailed Answer:
Hello madam,

Thank you for your appreciation and follow-up.

Role of complement system in carcinogenesis is controversial.

It is true that some products released by cancer cells can activate alternate pathway of complement system. (I would suggest you to review complement system and its activation pathways).

It is also true that MAC (Membrane attack complex) is the final product of complement cascade activation, which causes destruction of cells by making pores in cell membranes thus causing cell lysis.

However, in carcinogenesis, the evidence is contradictory. On other side, there is also evidence that activation of complement cascade contributes to chronic inflammation and may assist growth mitotically active cells.

So at present it is not clear whether complement system actually controls or promotes carcinogenesis!

Therefore, so far I am not aware of any treatment of cancer which utilizes complement system.

I am not aware of superior combat cells. But yes, I would agree that role of immune system in carcinogenesis is very interesting and complex.

As an example, I can think of role of intracystic administration of BCG vaccine for urinary bladder cancer. This is utilization of immune system for treatment of cancer. On other side, as you said, immune system can assist carcinogenesis.

By the way, my knowledge in oncology is very basic only.

Hope my answer will be helpful to you.

Thank you & Regards,

Dr Parin N Parmar

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Brief Answer:
It is much more complex than it seems

Detailed Answer:
Hello madam,

Thank you for your appreciation and follow-up.

Actually, the whole immune system, especially, the acquired immune system is very very complex.

Of course, the normal immune cells do not have proteins that make them susceptible to recognition and destruction.

But the process of recognition is also very complex. It takes interactions between antigen presenting cells, T-lymphocytes (helper cells), and other types of cells also.

Thus one type of cell along with another types of cell can jointly give signals to destructive cells. So many complex reactions occur before actual destruction of a foreign cell occurs. This much care is taken by nature so that self-cells are not falsely destructed as well as foreign harmful cells are not escaped from destruction.

Despite such great care, of course, something can go wrong and that is converted into cancer or autoimmune disorders or allergic disorders.

Hope above answer will be helpful to you.

I am sure you will find the whole immune system and its processes very interesting.

Wish you all the best.

Thank you & Regards,

Dr. Parin N. Parmar

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