Immune system questions

Two questions regarding the specific immune system:

Firstly, I understand that B-cells require activation before they become Plasma cells or memory cells. And I know they can be activated by helper T-cells, and also by antigen presenting macrophages. But do they require BOTH of these activation steps to be 'activated'. Or will one suffice?

Secondly a related question; T-cells and B-cells recognise antigens that are presented on the surface of macrophages, but can the recognise antigens WITHOUT the aid of macrophages? So can a T or B Cell recognise a pathogen without the pathogen first being engulfed by a macrophage and its antigen presented?

Thanks

Reply 1

Neon-Soldier32

13

First: Helper T cells release interleukins which activate the B cells. These are secreted when an antigen presenting cell (which includes macrophages presenting non self antigens and virally infected cells and cancer cells) so no, both aren't required as they both result in interleukins being secreted.

Second: Yes. Cells present antigens on their cell surface membrane and they are a protein which identifies them. If cholera enters your body it will present an antigen identifying it as cholera. Cholera presents this antigen without being engulfed by a macrophage. Macrophages presenting non-self antigens is just one way in which a response can be initiated.

Reply 2

Jimmy20002012

4

Original post by Neon-Soldier32

First: Helper T cells release interleukins which activate the B cells. These are secreted when an antigen presenting cell (which includes macrophages presenting non self antigens and virally infected cells and cancer cells) so no, both aren't required as they both result in interleukins being secreted.

Second: Yes. Cells present antigens on their cell surface membrane and they are a protein which identifies them. If cholera enters your body it will present an antigen identifying it as cholera. Cholera presents this antigen without being engulfed by a macrophage. Macrophages presenting non-self antigens is just one way in which a response can be initiated.

Just to clarify is this the way B cells are activated:

Receptors on B cells are specific and are complementary to that of the antigens presented on the cells/macrophages

The t helper cell which bind to the B cell

This causes the activation of B cells

The B cells, differentiate, profiliate into plasma cell which secretes antibodies specific to that antigen which kill and destroy them

Some B cells develop into memory cells which circulate in the blood in readiness if the same antigen enters the body again, which produces a secondary response

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Reply 3

Revd. Mike

17

Original post by byebyebadman

Secondly a related question; T-cells and B-cells recognise antigens that are presented on the surface of macrophages, but can the recognise antigens WITHOUT the aid of macrophages? So can a T or B Cell recognise a pathogen without the pathogen first being engulfed by a macrophage and its antigen presented?

Thanks

T-cells recognise antigen when presented on MHC molecules, so when presented by an antigen presenting cell (B cell, dendritic cell, macrophage), or on the surface of a virally infected cell.

Immune system questions

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