www.ebmt.org HLA and more Ilias I.N. Doxiadis Geneva 03/04/2012
HLA and more HLA and more / Doxiadis 2
Topic of the day Compatibility testing is a type of testing used to ensure compatibility of the system/application/website built with various other objects such as other web browsers, hardware platforms, HLA and more
KISS = Keep It Short and Simple
What is HLA? Human Leukocyte Antigens Expressed on almost all nucleated cells (red cells have remains of some HLA molecules (Blood group BG = HLA-B7; platelets express HLA (megakaryocytes ) Plays a key role in immune response (navel of the immune world) and in some other things
What is immunogenetics? Polymorphic (variable) genes involved in immune action Mendelian inheritance (green peas story of the Czech monk) Scientists on this field are enthusiastic!
HLA Originally detected as blood groups present on white blood cells (Human Leuk(c)ocyte Antigens) but present on almost all nucleated cells and platelets. More polymorphic than red blood groups: ABO system: 4 possible combinations (A,B,AB, O) HLA system: >1 million combinations (linkage disequilibrium)
HLA antigens (leading to an antibody production) ABO natural antibodies HLA only antibodies after confrontation (!) with foreign HLA antigens i.e. pregnancy, blood transfusion and transplantation (* post SCT problems)
1954: antibodies can cause leukocyte agglutination HLA: Human Leukocyte Antigens
Complement-dependent cytotoxicity
Negative reaction Positive reaction CDC
Serological difference between HLA-B35 and B53 B*35:01 = B35 (Bw6) AA pos. 77 80 81 82 83 B*35:01 B*53:01 Ser Asn Leu Arg Gly Asn Ile Ala Leu Arg B*53:01 = B53 (Bw4)
Human Leucocyte Antigens DNA Typing: DNA (from any suitable source) is amplified using specific primers. The needed level of resolution defines the method to be used.
Allelic difference between HLA-B*35 and B*53 N 77 80 81 82 83 B*35:01 AGC AAC CTG CGC GGC B*53:01 AAC ATC GCG CTC CGC
Polymorphism of the HLA system A C B DR DQ DP Specificities: A*01 B*51 DR*01 A*02 B*07 DR*15 A*03 B*08 DR*03 A*11 B*44 DR*04 A*69 B*15 DR*07 etc etc etc
Chromosome 6 A C B Chromosome 15 HLA class I molecules present on all nucleated cells and platelets Beta-2 microglobulin
Chromosome 6 DR DQ DP α β α β α β HLA class II molecules, mainly expressed on antigen presenting cells: dendritic cells, monocytes, B-cells and activated T cells
A1 B8 DR3 A3 B7 DR2 A2 B12 DR4 A9 B60 DR5 A1 B8 DR3 A3 B7 DR2 Genetics of HLA: mendelian inheritance; codominant expression Haplotype: Phenotype: Genotype: set of HLA genes on one chromosome set of antigens expressed on the cells set of genes on the DNA
a b c d a c a d b c b d 25 % HLA haploidentical 25 % 50 % HLA identical a c HLA different
The HLA system
>7,000 HLA alleles
monomorphic sites
T cell recognizes target cell T cell starts to destruct target cell Function Lysis of target cell
Role of HLA in the immune response patient IgG antibodies B APC HLA II CD4+ T helper T cell HLA I CD8+ T cytotoxic T cell
HLA class I /self peptide No recognition CD8+ T cell
Viral protein virus HLA class I /viral peptide Recognition CD8+ T cell
Self protein APC HLA class II Not recognized CD4+ T cell
virus APC HLA class II Activation CD4+ T cell
Clinical consequence of HLA polymorphism Viral protein Viral peptide HLA-A1 HLA-A2 HLA-A3 HLA-A11 + + + --
Polymorphism HLA is clinically relevant Different HLA molecules bind different peptides presented to T cells HLA associations with infectious diseases (e.g. B53) HLA associations with auto-immune diseases i.e. ankylosing spondylitis (B27), diabetes, rheumatoid arthritis
Question: How and why did MHC polymorphism evolve? Characteristics of MHC molecules: Enormous polymorphism Consequence: differential binding of antigenic peptides and differential immune response to pathogens. Increased incidence of heterozygosity Consequence: more possibilities for peptide binding and broader immune response
Analysis of HLA alleles in different populations
New HLA class I alleles in Amerindians Variation is induced in the groove Hypothesis viral pressure leads to selection new alleles
Gene frequencies HLA class I alleles survivors versus controls 16 14 12 10 8 6 survivors controls 4 2 0 A30 B7 B12 B17
Gene frequencies HLA class II alleles survivors versus controls 30 25 20 15 10 survivors controls 5 0 DR2 DR4 DR12 DR13
mismatches / matches / incompatibilites
What is a mismatch? P: HLA-A1, A2; B7, B8; DR2, DR3 D: HLA-A1, A2; B7, B15; DR2, DR3 MM? P: HLA-A1, A2; B7, B8; DR2, DR3 D: HLA-A1,-; B7, B8; DR2, DR3 MM? P: HLA-A1, A2; B7, B8; DR2, DR3 D: HLA-A3,-; B7, B8; DR2, DR3 MM?
What is a mismatch? P: HLA-A1, A2; B7, B8; DR2, DR3 D: HLA-A1, A2; B7, B15; DR2, DR3 MM? D > P no P: HLA-A1, A2; B7, B8; DR2, DR3 D: HLA-A1,-; B7, B8; DR2, DR3 MM? D > P yes P: HLA-A1, A2; B7, B8; DR2, DR3 D: HLA-A3,-; B7, B8; DR2, DR3 MM? D > P yes
SCT T cell mediated response By introduction of incompatibilties humoral response possible Post transplantation treatment of the patient requires the control of HLA specific antibodies in the donor and the patient
Immunogenetics and.. fun
Rhodents prefer partners with dissimilar MHC Different H-2 80% Recognition based on odour: H-2 identical 20% similar results when urine is used Yamazaki et al., 1979
Do the MHC genes play a role in partner choice?
MHC-dependent mating preferences in man (Wedekind et al., 1995) Female (N=49) and male students (N=44) were typed for HLA-A,-B and DR. The male students had to use neutral soap and no after-shave etc. Each male student wore a T-shirt for two consecutive nights. Next the T shirts were collected but not washed
T-shirts are put in a box and females are asked to smell Each women is asked to judge the odour of 7 T-shirts: 3 of man with a similar HLA type. 3 of man with a dissimilar HLA type. 1 control (fresh) T shirt.
Females prefer odour of males with dissimilar HLA types very nice 6 5 4 3 2 Pill using women 1 terrible 0 HLA dissimilar HLA similar HLA dissimilar HLA similar Wedekind et al.,1995
Females prefer odour of males with dissimilar HLA types very nice 6 5 4 3 2 Pill using women 1 terrible 0 HLA dissimilar HLA similar HLA dissimilar HLA similar Wedekind et al.,1995
Summary and conclusions To work in the field of immunogenetics is really rewarding The function of the molecules is the immune surveillance towards pathogens Transplantation reflects all attributesof immunity Among all these factors is HLA one of the major components.
Stem cells and diseases.
The end! Thank you