I guess you are focused on allografts as you refer to human organ transplantation.  Historically, acquired immune response have been the focus with early work flagging up cytotoxic T cells.  The role of CD4 helper cells was then teased out a bit.  It gets a bit more complicated here as CD4 effector cells having direct effects creep in but I'm going to confine myself to mainstream pathways as a start.  The CD4 helpers can support macrophage mediated DTH responses, an often overlooked pathway.  They also support antibody responses.  This is again a difficult area as not all antibodies cause graft damage and this is not always hyper acute/acute damage,  But I would say as a simple starting point we have cytotoxic T cell response and CD4 supported DTH responses and antibody responses: 3 mechanisms so far!  Turning to innate immunity, this is again often overlooked, but very important.  All the basic inflammatory responses are important and can significantly damage grafts.  NK cells should not be forgotten either!  There is a great review in Ann Rev Imm from about 1986 by Mason and Morris that puts all this in context.  It describes the initial inflammatory damage to experimental skin grafts, but grafts often survive this and settle down.  More sensitive tissues (eg islets of Langerhans) may not survive this.  So innate and acquired important with a number of major players contributing to varying degrees.

Looking at this from a different angle, within the acquired response, there are two methods of presentation of HLA antigen to recipient T cells: The direct and indirect pathways.  I won't go in to this here, but important to be aware that both exist.

Furthermore, these 'cellular' pathways may then recruit a number of different pathways to actually cause damage.  In addition to those mentioned above, consideration of perforin and granzyme is important for T cell killing.

Finally, all graft damage is not necessarily rejection: hypoxia and ischaemia reperfusion injury are important and tissue specific mechanisms such as glomerular hyper filtration in kidney transplants contribute also.

Hope this helps.  There are a number of references on my RG page that discuss aspects of this further.

I suppose that depends on your criteria of pathway-- if you want a finite "number" of pathways. In theory, graft rejection is caused by innate or adaptive immune responses so I suspect any pathway that differentiates between "self" and "foreign" and any pathways involved in the negative physiological response to the "identity" of the transplanted organ would be responsible. Off the top of my head, I suspect TLRs, TNFRs, and SAPK/JNK play a major role in these processes. If you rewrite your question to be more specific and quickly answered I am sure someone more familiar with the topic would be able to give better insight.

Cheers

Autograft, allograft, autograft and xenograft are methods used in transplantation, there are two pathways to identify rejection one is self and non self, cross re activity and degeneration and no selection of foreign cells and tissues. Yes, TLRs, TNFRs, and SAPK/JNK , and calcium regulatory proteins also might play important role in graft rejection.

I guess you are focused on allografts as you refer to human organ transplantation.  Historically, acquired immune response have been the focus with early work flagging up cytotoxic T cells.  The role of CD4 helper cells was then teased out a bit.  It gets a bit more complicated here as CD4 effector cells having direct effects creep in but I'm going to confine myself to mainstream pathways as a start.  The CD4 helpers can support macrophage mediated DTH responses, an often overlooked pathway.  They also support antibody responses.  This is again a difficult area as not all antibodies cause graft damage and this is not always hyper acute/acute damage,  But I would say as a simple starting point we have cytotoxic T cell response and CD4 supported DTH responses and antibody responses: 3 mechanisms so far!  Turning to innate immunity, this is again often overlooked, but very important.  All the basic inflammatory responses are important and can significantly damage grafts.  NK cells should not be forgotten either!  There is a great review in Ann Rev Imm from about 1986 by Mason and Morris that puts all this in context.  It describes the initial inflammatory damage to experimental skin grafts, but grafts often survive this and settle down.  More sensitive tissues (eg islets of Langerhans) may not survive this.  So innate and acquired important with a number of major players contributing to varying degrees.

Looking at this from a different angle, within the acquired response, there are two methods of presentation of HLA antigen to recipient T cells: The direct and indirect pathways.  I won't go in to this here, but important to be aware that both exist.

Furthermore, these 'cellular' pathways may then recruit a number of different pathways to actually cause damage.  In addition to those mentioned above, consideration of perforin and granzyme is important for T cell killing.

Finally, all graft damage is not necessarily rejection: hypoxia and ischaemia reperfusion injury are important and tissue specific mechanisms such as glomerular hyper filtration in kidney transplants contribute also.

Hope this helps.  There are a number of references on my RG page that discuss aspects of this further.

Dear colleague Dr. Rashid

In my book entitled "Transplantation of Kidney" issued in 2004 years!

author Jasenko Karamehic and Associates

You have the answers to questions, rejection of kidney, their prevention and treatment of rejection of their different pathogenesis, immunosuppressive therapy protocols or kidney and relates to your interest in the legal and educational process in this area!

The book is supplied in electronic form in my bibliography on my side on Reaserch Gate.

Best Wishes

Jasenko

Dear colleagues dr.Rashid

Also, and this my book entitled Transplant Immunology "issued in 2010 years!

author Jasenko Karamehic and Associates

You have the answers to questions you have to answer the pathogenesis of immune rejection of organs and for immediate treatment issues in organ transplantation, immunosuppressive therapy protocols and relates to your interest in the legal and educational process in this area!

The book is supplied in electronic form in my bibliography on my side on Reaserch Gate.

Best Wishes

Jasenko Karamehic

Dear colleagues dr.Rashid

In my book titled authors Jasenko Karamehic and associates "Transplants Kidney and Pancreas Clinical and immunological aspects of pharmacotherapy" issued in 2012 years:

You have the answers to questions you have to answer the pathogenesis of immune rejection of organs in this case, kidney and pancreas and their rejection treatment and prevention issues in organ transplantation, immunosuppressive therapy protocols and relates to your interest in the legal and educational process in this area!

The book is supplied in electronic form in my bibliography page on Reaserch Gate.

regards

Jasenko

Dear colleagues dr.Rashid,

Also, and this my book entitled The immunosuppressive therapy and its use in organ transplants "issued in 2012 years!

author Jasenko Karamehic, Sebija Izetbegovic and Associates

you have the answer to issues in organ transplantation, described in detail the pathogenesis of formation episodes of organ rejection with various aspects of immunosuppressive therapy protocols for the treatment of rejection episodes and body relates to your interest in the legal and educational process in this area!

The book is supplied in electronic form in my bibliography on my side on Reaserch Gate.

Best Wishes

Jasenko Karamehic

Dear colleagues dr.Rashid,

Also, and this my book entitled Clinical Immunology "issued in 2007 years!

author Jasenko Karamehic, Zehra Dizdarevic and Associates in section 6 below

entitled "Transplantation Immunology" in chapter 39:

under the title

"Immune aspects of organ rejection"

and Chapter 40 entitled:

"The immune response to the transplanted organ"

you have the answer to issues in organ transplantation, described in detail the pathogenesis of formation episodes of organ rejection with various aspects of immunosuppressive therapy protocols for the treatment of rejection episodes and body relates to your interest in the legal and educational process in this area!

The book is supplied in electronic form in my bibliography on my side on Reaserch Gate.

Best Wishes

Jasenko Karamehic

Dear colleagues dr.Rashid,

I forgot to mention the other sections pertaining to your questions for etipathogenesis organ rejection after organ transplantation but, there are also, and this my book entitled Clinical Immunology "issued in 2007 years!

author Jasenko Karamehic, Zehra Dizdarevic and Associates in section 6 below

entitled "Transplantation Immunology" in sections 28,33,34,35,36, 37,38:

under the headings:

28. - "Transplantation Immunobiology"

32 "Adult Kidney Transplantation"

34 .- "Pediatric Kidney Transplantation"

35 .- "Lung transplantation"

36. "Bone Transplantation"

37.- "Transplantation and Central Nervous System"

38. "The Tearapy of immunosuppressants and Management and Clinical Immunology"

you have the answer to issues in organ transplantation, described in detail the pathogenesis of formation episodes of organ rejection with various aspects of immunosuppressive therapy protocols for the treatment of rejection episodes and body relates to your interest in the legal and educational process in this area!

The book is supplied in electronic form in my bibliography on my side on Reaserch Gate.

Best Wishes

Jasenko Karamehic