An In-vitro Standardization of B Cell Elispot Assays

• To optimize an in-vitro assay to enumerate HLA-specific memory B cells in order to monitor efficacy of desensitization protocols. [ Time Frame: Enrollment (baseline), midpoint of desensitization (only if receiving high dose IVIg); prior to transplant; 3, 6, 12 and 24 months post-transplant. ] [ Designated as safety issue: No ]
  B cells will be tested for their ability to produce IgG and tetanus antibodies (as controls) and HLA specific antibodies corresponding to those detected by the flow PRA assay. In subjects not undergoing desensitization, 3 tubes (30 ml) of blood will be drawn twice (total of 60 ml blood taken) 8-12 weeks apart. In subjects undergoing desensitization 3 tubes (30 ml) of blood will be taken at 7 points; enrollment, anticipated midpoint of desensitization, prior to transplant, 3, 6, 12 and 24 Months post-transplant (total of 210 ml blood taken).
  
  

• Evaluate the relationships between antibody strength, measured by flow cytometry, number of memory B cells in circulation of highly sensitized patients awaiting organ transplant or undergoing desensitization procedures to facilitate organ transplant. [ Time Frame: Enrollment (baseline), midpoint of desensitization (only if receiving high dose IVIg); prior to transplant; 3, 6, 12 and 24 months post-transplant. ] [ Designated as safety issue: No ]
  B cells will be tested unstimulalated or stimulated with a cocktail of CpG, anti-CD40-L, IL-10 and IL-4.
  
  

Sensitization to HLA antigens is the main barrier to solid organ transplantation. Currently, HLA sensitization is monitored by testing patients' serum against a panel of HLA antigens (whether those will be presented on cell surface or on solid phase matrixes) and calculating the % of positive responses. Such result give indication of the relative breadth of sensitization but not on it "depth" - the relative strength of specific antibodies, nor does it provide any information regarding the memory B cells / plasma cells that can manufacture a specific HLA directed antibody.

This is a single center study to evaluate and optimize the use of in-vitro assay to enumerate B cells producing human leukocyte antigens (HLA)-specific antibodies. The proposed assay is based on principles used for enumeration of specific cytokine producing memory T cells - an ELISPOT assay. The investigators are currently using the T cell ELISPOT assay in our laboratory.

The investigators believe that the proposed assay will provide biologically relevant immune measures that are crucial for the long term outcome of transplantation in highly sensitized patients.

Highly sensitized patients encompass a high risk patient group among transplant recipients. The proposed assay is designed to predict the fate of DSA producing (or capable of producing) memory and plasma cells. Thus, it should allow prediction and early detection of activation of the humoral arm of the immune system, specifically against the donor. This, in turn, may prompt early intervention and preservation of the allograft. Three tubes of blood will be drawn twice, 8-12 weeks apart, during clinic or standard of care dialysis visits following optimization. Subjects undergoing desensitization will have three tubes of blood drawn seven times over the course of two years for the analysis.