Immunology 2011 Lecture 11 Innate Immunity & Genetics of Inbreeding. 6 October

Transcription

1 Immunology 2011 Lecture 11 Innate Immunity & Genetics of Inbreeding 6 October

2 HANDOUT #6, Problem Set 3 TODAY Innate Immunity no core notes Genetics of Inbreeding - Appendix 10 MHC & Transplantation, Chapter 11

3 Ag/Ab complexes ANTIGEN Complement Killing of bacteria Inflammation Inactivation of viruses APC Allergy Antigen processing (dendritic cells, MΦ et al.) Antigen "presentation" Antigenspecific triggering B T Proliferation Differentiation T H2 T-cell "help" AFC ANTIBODY T-CELL FUNCTIONS TC T-cell killing: virus-infected cells, transplants AUTOIMMUNITY Adaptive Immunity: Clonally precommitted cells & effector mechanisms T H1 Mixed Lymphocyte Reaction (MLR) Delayed type hypersensitivity, (DTH); e.g. tuberculin reaction T reg Tolerance, suppression AFFERENT CENTRAL EFFERENT THREE "LIMBS" OF THE IMMUNE RESPONSE

4 Innate Immunity Physical barriers: skin, mucous/ciliary membranes, etc. Phagocytosis: macrophages, PMNs RES, reticuloendothelial system specific receptors for microbial cell wall products Complement et al (lysis, opsonization) Non-adaptive: no memory, no generation of receptor diversity as for Ig & TcR

5 Innate Immune Response to Salmonella in Gut Can be killed by defensins produced by crypt cells of the gut (large family of small peptide toxins). Organisms and antigens transported intact into gut mucosa and circulation by specialized M -cells. Organisms can activate macrophages via TLR binding, stimulates phagocytosis and killing. Fixation of complement by alternate & MBL pathways, opsonization & lysis. (Adaptive response later produces Ab, C-fixation by classical pathway, opsonization & lysis, etc.)

6 Innate Immunity: Toll-Like Receptors (TLR) Vertebrate homologs of Drosophila Toll-receptors, part of innate immunity, >13 members in mammals. Mycobacterial polysaccharides bind to TLR-2 on macrophages, stimulates internalization, activation. LPS and other microbial products stimulate TLR-4 signaling pathways in lymphocytes and macrophages. specialized & highly selective but non-adaptive recognition of microbial products (no clonal generation of diversity, no anticipation)

7 Relation Between Innate and Adaptive Immunity Physical barriers: skin, mucous membranes, etc. Secretory IgA Phagocytosis: macrophages, DCs, PMNs Opsonizing Ab Complement: Alternate & MBLectin Classical & alternate C-fixation by Ab/Ag Ag-processing & presentation by activated tissue dendritic cells or other APCs is required for initiation of adaptive responses

8 ****************************** Genetics of Inbreeding Genetic compatibility is required for allograft survival & cell/cell interactions in immune responses Natural populations are genetically heterogeneous, limiting experimental & clinical manipulations.

9 Ag/Ab complexes ANTIGEN Complement Killing of bacteria Inflammation Inactivation of viruses APC Allergy Antigen processing (dendritic cells, MΦ et al.) Antigen "presentation" Antigenspecific triggering B T Proliferation Differentiation T H2 T-cell "help" AFC ANTIBODY T-CELL FUNCTIONS TC T-cell killing: virus-infected cells, transplants AUTOIMMUNITY MHC T H1 Mixed Lymphocyte Reaction (MLR) Delayed type hypersensitivity, (DTH); e.g. tuberculin reaction T reg Tolerance, suppression AFFERENT CENTRAL EFFERENT THREE "LIMBS" OF THE IMMUNE RESPONSE

10 SPLEEN CELLS NORMAL SPLEEN DONOR ANTIGEN 900R TEST SPLEEN FOR Ab-FORMING CELLS AT DAY 7 IRRADIATED RECIPIENT ADOPTIVE TRANSFER Success of adoptive transfer relies on genetic compatibility between donor and recipient Uniformity of genetic background is important in all biological and biomedical research

11 Importance of Inbred Strains "The introduction of inbred strains into biology is probably comparable in importance with that of the analytical balance into chemistry." (Hans Gruneberg, 1952) "...the development of inbred strains has constituted probably the greatest advance in all cancer research." (W.E. Heston, 1963)

12 PROPERTIES OF INBRED STRAINS Genetically uniform, all individuals are identical Homozygous at all loci No rejection of tissue & organ grafts between members of the strain May be bred to express traits useful for models of human disease

13 How to create an inbred strain: Begin with two random individuals and breed them. Parents: Aa X Aa Offspring (F 1 ) AA Aa aa aa Frequencies: AA:25% Aa: 50% aa: 25% breed brother & sister for next generation

14 The Next (F2) Generation... probability of cross next generation AA X AA 1/16 offspring all AA p=1/16 AA X Aa 1/4 AA X aa 1/8 offspring varied Aa X Aa 1/4 Aa X aa 1/4 aa X aa 1/16 offspring all aa p=1/16* * * 12.5% (1/16 + 1/16) uniformly homozygous 12.5% of all genetic loci will become homozygous......at each generation

15 After 20 generations... Coefficient of Inbreeding = 98.5% This is the formal definition of inbred strain Guinea pigs were first inbred in 1906, mice & rats in 1909, Some strains have been inbred for well over 200 generations. >80 mouse strains (C57Bl/6, DBA/2 etc.) >100 rat strains Also hamsters, chickens, rabbits. Can also impose selection during inbreeding. Varying incidence of tumors, dental caries, high or low blood pressure, etc.

16 PROPERTIES OF INBRED STRAINS: 1) Genetically uniform ( isogenic ; like human twins) 2) Homozygous at all loci (unlike human twins) 3) "Breeds true" May be delicate and of limited fertility. Recessive traits may be fixed. (note dangers of inbreeding in human populations) Random selection of brother/sister may not be so random

17 F1 INBRED CROSSES: e.g. (C57Bl/6 x DBA/2)F1, "B6D2F1" 1) Genetically uniform ( isogenic ; like human twins) 2) Not homozygous at all loci (like human twins) 3) Does not breed true Often more hardy, "hybrid vigor".

18 CONGENIC STRAINS Pairs of inbred strains which differ from one another at a single genetic locus. BALB/c-H-2 b (vs. H-2 d ) C57BL/6-Ig s (vs. Ig b ) C57BL/6-db (vs. +[wt]) etc.