Immunoadsorption

Platelet IgG antibodies and the circulating immune complex may attribute to the disease progression in patients of idiopathic thrombocytopenic purpura or thrombotic thrombocytopenic purpura. Therapeutic removal of IgG and circulating immune complex by passing patient's plasma through column of Protein A derived from Staphylococcus aureus is available and is considered as palliative.


Irradiation of Blood/Blood Product

Viable lymphocytes which are present in blood and blood products may initiate lethal transfusion-associated graft versus host disease (TA-GvHD) in immuno-compromised patients. Ablation of the viable lymphocytes in blood and blood products by g -irradiation prevents TA-GvHD in post-BMT patients.


Leucopheresis

Leucopheresis is a process to remove circulating nucleated cells in blood. In leukaemic patients with high white blood cell count of approximately 500 x 10⁹/L, leucophereses are performed to avoid the adverse or fatal effect of chemotherapy-initiated tumour lysis.


Long Term Bone Marrow Culture

HPSC which are capable of reconstituting long-term haemopoiesis in post-BMT patients are cells with prominent self-renewal potential. These cells, long term bone marrow culture-initiating cells, can be maintained in liquid culture for 8 to 12 weeks, and they are also considered as cells closest to the pluripotent HPSC. Long term bone marrow culture provides a quantitative means to assess the pluripotent HPSC in vitro.

Lymphokine Activated Killer Cell Generation

Adoptive immunotherapy utilizing lymphokine activated killer cells holds great clinical promise for the treatment of cancer. Basically immune cells of the tumour-bearing patients are ex-vivo activated and generated by cultivation in tissue culture medium containing high concentration of interleukin-2 for a number of days, and are then reinfused to the patients. The activated immune cells (lymphokine activated killer cells) which have anti-tumour reactivity can mediate direct and indirect anti-tumour effects to combat the tumour.

Peripheral Blood Stem Cell Collection

Circulating HPSC can be found in peripheral blood of patients in the natural recovery phase after marrow-toxic therapy. Mobilization with haematopoietic growth factors in patients further augments the circulating quantities. Recently allogeneic peripheral blood stem cells mobilized with cytokines in normal donors emerge as an alternative of HPSC in BMT. Blood from patient/donor mobilized with cytokine is drawn into a cell separator which separates blood into plasma, buffy coat and red blood cells by means of physical centrifugation. HPSC which are of similar physical property of mononuclear cells in the buffy coat are harvested, while the plasma and red blood cells are returned to patient/donor via another vascular access. Normally 2 to 3 times blood volume of a patient/donor are processed within 3 hours.

Plasmapheresis

It is a therapeutic modality to exchange the circulating pathogenic substance(s) in patient’s plasma by inert solutions of electrolytes, human albumin or normal plasma. Plasmapheresis to remove ABO antibodies is applicable to patients for major ABO-mismatched BMT.


Positive Selection of CD34+ Cells

HPSC which inherit the cellular marker CD34 present in small quantity in marrow and peripheral blood stem cell collection. Positive selection of CD34+ cells is an effective means for reducing the volume of HPSC and hence reducing the toxicities related to reinfusion. It is also applicable to reduce the number of tumour contaminating cells and T-cells in autograft and allograft respectively.

Red Blood Cell Depletion

In major ABO-mismatched BMT, ABO antibodies in recipient’s circulation will bind to donor’s red blood cells in the allograft and lead to acute haemolytic transfusion reaction. Red blood cells in the allograft are removed by physical means, hence intravascular haemolytic transfusion reaction due to major ABO-mismatched marrow transplantation is avoided.


Residual Disease Monitoring

Disease relapse remains a major problem in post-BMT patients. When patients are in clinical remission, the ability of conventional methods to detect residual disease is limited. With the advent of molecular biology, monitoring of minimal residual disease in leukaemic patients with specific markers can be achieved. The application of polymerase chain reaction to amplify leukaemia-specific chromosomal translocations, clone specific immunoglobulin gene rearrangement and T-cell receptor gene rearrangements allows assessment of the disease status and the prediction of disease relapse prior to any clinical presentations.


T-cell Depletion and Manipulation

The primary obstacle associated with allogeneic BMT is graft versus host disease (GvHD). This results from the recognition of disparate minor histocompatibility antigens (HLA) on the recipient’s cells by immuno-competent T cells in the allograft despite major histocompatibility complexes are matched. T-cell Purging and manipulation are graft engineerings to alleviate GvHD in HLA-mismatched or haploid-identical BMT.

Thawing and Re-infusion

Cryopreserved marrow, umbilical cord blood and peripheral blood stem cell collection which are stored in liquid nitrogen are thawed bedside and immediately reinfused to the patients.


Tumour Cell Purging

Autologous BMT are often performed in patients without HLA-matched allografts. Bone marrow/peripheral blood stem cells are collected from patients in clinical remission, cryopreserved, stored in liquid nitrogen and reinfused following high-dose chemotherapy. However micro-metastasis to bone marrow may attribute occult tumour cells to autograft. Tumour cell purging of autograft decontaminates and eradicates any residual tumour cells that may lead to autograft-mediated disease relapse.


Viability Test

Viable cells with intact membrane integrity do not allow the influx of dye and hence will not be stained. Trypan blue dye exclusion test is used to differentiate viable and non-viable nucleated cells and is often employed in the quality control of manipulated and processed marrow. Having counted the stained cells, the percentage of cell viability of a given sample can be easily enumerated.