|M.Sc Student||Mory Adi|
|Subject||Immunodeficiency Syndromes - Clinical and Molecular|
|Department||Department of Medicine||Supervisors||Clinical Professor Ruth Gershoni-Baruch|
|Professor Emeritus Amos Etzioni|
Primary immunodeficiencies are rare disorders caused by intrinsic defects of the immune system.
The primary objective of this research was to identify the genetic defect in patients with primary immunodeficiencies and to establish a plausible correlation between their clinical and molecular characteristics. Twelve children affected altogether with one of five different diseases were available for study.
These include: X-linked Agammaglobulinemia (XLA), Leukocyte adhesion deficiency type I and type II (LAD I & LAD II), Hyper IgM Syndrome (HIGM) and Wiskott Aldrich syndrome (WAS) .
Methodology: A molecular investigation, tailored to match the clinical diagnosis, was devised for each patient independently. Altogether molecular analyses employed PCR, RFLPs, DHPLC (denaturating high performance liquid chromatography) and sequencing technology. Five candidate genes were screened in a multistep analysis.
Results: Altogether nine mutations `were identified in eight patients, including four new previously unreported mutations and five mutations previously described by others.
The mutations identified, together with the reported in the literature, allow us to define a phenotype-genotype correlation.
Missense mutations detected in patients with LADI and LADII were restricted to conserved sequences, in line with those previously reported. It is postulated that genetic variations located in other regions of the gene, although inherently present in individuals from the general population, do not cause a disease but rather somehow impinge on one’s so-called normal immunity.
A deletion encompassing two exons in BTK, no doubt disrupting the structure of the protein, caused a mild disease in our patient with XLA but was otherwise lethal to other family members, who died in infancy, bringing back to light the concept that every genetic disease or trait, and the immune response in particular, involve a complex interplay between environmental and human (genetic and non-genetic) factors.
Two splicing mutations were identified in two WAS patients. Here again, the mutations described majorly disrupt the protein WASP. The concept that the WAS phenotype, which may vary from isolated thrombocytopenia to severe classic lethal immunodeficiency is “mutation” dependent was confirmed.
In two of the four patients in whom no mutations were detected, the diagnosis of HIGM syndrome was subsequently revised.
With this in mind, the concept, that immunodeficiency is a rare condition, should be reconsidered. The criteria for normalcy, in a system, are based on the immunologic phenotype, related to population distribution of laboratory data. It is clear that we still have incomplete knowledge regarding how the organism as a whole, including the immune system, protects itself from infection.