What is HLA and Why It Matters in Kidney Transplantation

Updated: June 2025 | By IranSurgeryCenter

Introduction

One of the key factors for a successful kidney transplant is ensuring immune system compatibility between the donor and recipient. Human Leukocyte Antigens (HLA) play a vital role in helping the immune system distinguish between self and foreign tissues. Better HLA matching can significantly improve kidney graft survival and reduce the risk of rejection.

What is HLA?

HLA are proteins found on the surface of most cells. They act like ID tags, helping the immune system recognize the body’s own cells. If the HLA on a donor kidney are too different from the recipient’s, the immune system may attack the new organ, leading to transplant rejection.

Important HLA Types in Kidney Transplant

There are three major HLA antigens considered in kidney transplantation:

HLA-A
HLA-B
HLA-DR

Each person inherits one HLA type from each parent, resulting in six key HLA markers. A full match is 6/6. Even a 3/6 match may be acceptable, but full matches are ideal.

Benefits of Good HLA Matching

Lower rejection risk: The immune system is less likely to attack the transplanted kidney.
Reduced need for immunosuppressive drugs: Lower doses may be sufficient.
Longer graft survival: Matched kidneys tend to last longer.
Fewer complications and lower costs: Less medication and hospitalization.

What Happens If HLA Is Not Well Matched?

If there is poor HLA compatibility:

Rejection is more likely, especially in the first 3–6 months.
Stronger immunosuppressive drugs like ATG or high-dose tacrolimus may be needed.
Increased risk of infection, diabetes, and other side effects.
Possible early graft failure and return to dialysis or need for re-transplantation.

Graft Survival Statistics Based on HLA Matching

Studies show a strong link between HLA compatibility and long-term graft survival. Here are average survival rates:

Donor Type	HLA Match	1-Year Survival	5-Year Survival	10-Year Survival
Living Donor	6/6 match	98%	90%	75%
Living Donor	3/6 or less	93%	75%	55%
Deceased Donor	6/6 match	95%	85%	70%
Deceased Donor	3/6 or less	89%	70%	50%

*Each additional HLA match may extend kidney lifespan by 2–4 years on average.

Can a Kidney Transplant Be Done Without Full HLA Match?

Yes. Thanks to advanced immunosuppressive therapies, successful transplants can occur even with partial or poor HLA matches. This is especially true when:

Blood type (ABO) is compatible
Crossmatch test is negative
Panel Reactive Antibody (PRA) levels are low
A tailored immunosuppressive protocol is followed

How Is HLA Testing Done?

HLA typing is performed using a blood sample from both donor and recipient. This test is often done alongside PRA and crossmatch testing to evaluate transplant compatibility.

Conclusion

HLA matching plays a crucial role in kidney transplantation. Better HLA compatibility leads to lower rejection risks, fewer medications, longer graft survival, and improved quality of life. However, even with partial mismatch, kidney transplant is possible with proper medical planning and support.