The Single Antigen Bead Assay (SAB) is a highly sensitive and specific immunological technique used in the field of transplant medicine to assess the compatibility between a donor's organ or tissue and a recipient's immune system. This assay is particularly employed in the context of solid organ transplantation, such as kidney or heart transplants. The SAB assay involves the use of microscopic beads, each coated with a single known antigen. Antigens are molecules that can induce an immune response in the body. In the case of transplantation, the goal is to identify the presence of antibodies in the recipient's serum that may react with antigens present on the donor's cells. The antigens chosen for coating the beads are typically representative of human leukocyte antigens (HLA), which play a crucial role in immune recognition. During the assay, the patient's serum is incubated with a panel of these antigen-coated beads. If antibodies specific to the antigens are present in the serum, they will bind to the corresponding beads. The binding can then be detected through various methods, such as fluorescence, allowing for a precise determination of the antibodies present and their specificity. The results obtained from the SAB assay are crucial in evaluating the risk of rejection in organ transplantation. A high level of antibody reactivity against the donor's antigens may indicate a higher risk of rejection, whereas a lower reactivity suggests better compatibility. This information helps clinicians make informed decisions about organ compatibility, tailor immunosuppressive therapy, and improve the overall success of transplantation procedures. The SAB assay has significantly contributed to the advancement of transplant medicine by providing a reliable and comprehensive tool for assessing immunological compatibility in transplant recipients.

1. Single Antigen Bead Assay
Presented by: Amit Kumar Bhardwaj | Chimera labs

2. INTRODUCTION
• SAB assays are an important part for the pre-transplant evaluation process and can help to identify
patients who are at high risk of transplant rejection. This information can be used to select
appropriate donors and to plan for transplantation.
• It also used to monitor patients after transplantation to detect the development of new HLA
antibodies. This information can be used to detect and treat rejection in early.
• The assay is highly sensitive and highly specific.
• It uses Specific antigen (HLA glycoprotein) coated polystyrene beads.
• The test is used to assess a patient's sensitization to donor HLA.

3. HUMAN LEUCOCYTE ANTIGEN (HLA)
• HLA are glycoproteins which are present on the surface of nucleated cells
• There are 2 major classes of HLA
• HLA Class I: A, B and C, Which are presented on all nucleated cells.
• HLA Class II: DR, DQ and DP, Which are presented on only APC (Antigen presenting Cells.)
• Immune System Recognition
• HLA antigens serve as identification markers on the surface of cells, allowing the immune system to distinguish
between self and non-self substances.
• They help immune cells recognize and respond to pathogens, including viruses, bacteria, and other foreign
invaders.
• Antigen Presentation:
• HLA molecules play a key role in presenting antigens to T cells, a type of immune cell.
• Antigens derived from pathogens or abnormal cells are displayed on HLA molecules, triggering specific immune
responses that help eliminate the threat.
• Transplant Compatibility:
• HLA matching is crucial in transplantation to minimize the risk of graft rejection.
• Matching HLA antigens between donors and recipients enhances the compatibility of transplanted organs or
tissues, reducing the likelihood of immune rejection.

4. Anti HLA Antibodies
Anti-HLA antibodies are antibodies produced by the immune system that
target human leukocyte antigens (HLA), which are proteins on the surface
of cells. These antibodies can be harmful particularly in organ
transplantation
1.Transfusions: Receiving multiple blood transfusions can expose a
person to foreign HLA antigens, leading to the development of anti-HLA
antibodies.
2.Previous Transplants: If someone has had a previous organ transplant,
their immune system may have been sensitized to foreign HLA antigens,
making it more likely to produce anti-HLA antibodies upon subsequent
transplants.
3.Pregnancy: During pregnancy, a mother can be exposed to the father's
HLA antigens, especially if there is a mismatch between the mother's and
father's HLA types. This exposure can sensitize the mother's immune
system, leading to the production of anti-HLA antibodies.
Once sensitized, the immune system remembers the specific HLA antigens
and can produce antibodies upon re-exposure. This sensitization can
complicate organ transplantation, as the presence of anti-HLA antibodies
increases the risk of organ rejection when a transplant is attempted.
Matching donors and recipients based on HLA compatibility helps reduce
the risk of anti-HLA antibody-related complications in transplantation.

7. Overview of SAB Assay
SAB assays use fluorescently labelled micro beads that are coated with specific HLA antigens. When a patient's
serum is added to the beads, any HLA antibodies that are present will bind to the beads. A fluorescently labelled
antibody is then added to detect the bound HLA antibodies. The amount of fluorescence is proportional to the amount
of HLA antibody present, so the fluorescence intensity can be used to quantify the level of HLA antibody.

8. RESULT

9. THANK YOU