A Genetic Herd‐Immunity Model for the Maintenance of MHC Polymorphism

Wills, Christopher; Green, Douglas R.

doi:10.1111/j.1600-065x.1995.tb00679.x

Cited by 74 publications

(31 citation statements)

References 57 publications

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“…Later research showed that density-dependence was very common in some tropical forests 6–8. An extension of the Janzen–Connell hypothesis, the species herd protection hypothesis, suggests that heterospecifc neighbors can promote coexistence by thwarting the transmission of biotic plant pests [7], [9]. According to the species-herd protection hypothesis, heterospecific crowding may be of general benefit for the survival of recently established seedlings because fewer encounters between a host and its species-specific pests and pathogens would occur [9]–[10].…”

Section: Introductionmentioning

confidence: 99%

Spatial Distribution and Interspecific Associations of Tree Species in a Tropical Seasonal Rain Forest of China

et al. 2012

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Studying the spatial pattern and interspecific associations of plant species may provide valuable insights into processes and mechanisms that maintain species coexistence. Point pattern analysis was used to analyze the spatial distribution patterns of twenty dominant tree species, their interspecific spatial associations and changes across life stages in a 20-ha permanent plot of seasonal tropical rainforest in Xishuangbanna, China, to test mechanisms maintaining species coexistence. Torus-translation tests were used to quantify positive or negative associations of the species to topographic habitats. The results showed: (1) fourteen of the twenty tree species were negatively (or positively) associated with one or two of the topographic variables, which evidences that the niche contributes to the spatial pattern of these species. (2) Most saplings of the study species showed a significantly clumped distribution at small scales (0–10 m) which was lost at larger scales (10–30 m). (3) The degree of spatial clumping deceases from saplings, to poles, to adults indicates that density-dependent mortality of the offspring is ubiquitous in species. (4) It is notable that a high number of positive small-scale interactions were found among the twenty species. For saplings, 42.6% of all combinations of species pairs showed positive associations at neighborhood scales up to five meters, but only 38.4% were negative. For poles and adults, positive associations at these distances still made up 45.5% and 29.5%, respectively. In conclusion, there is considerable evidence for the presence of positive interactions among the tree species, which suggests that species herd protection may occur in our plot. In addition, niche assembly and limited dispersal (likely) contribute to the spatial patterns of tree species in the tropical seasonal rain forest in Xishuangbanna, China.

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Section: Introductionmentioning

confidence: 99%

Spatial Distribution and Interspecific Associations of Tree Species in a Tropical Seasonal Rain Forest of China

et al. 2012

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“…Wills and Green (Wills and Green, 1995) have given us a reasonable framework for thinking about the problem of the selection pressures driving MHC polymorphism. If the genes encoding susceptibility to a given pathogen are expressed rarely as phenotypes in the population, then the pathogen can only spread to a limited extent.…”

Section: What Drives the Polymorphism Of The Mhc?mentioning

confidence: 99%

The Tritope Model for restrictive recognition of antigen by T-cells

Cohn

2008

Molecular Immunology

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Based on the Tritope model of the TCR (Cohn, 2005c), a set of functional and evolutionary problems surrounding restrictive recognition of antigen are discussed. These include the origin of allelespecific recognition, the selection pressures for polygeneism and polymorphism, the TCR signaling interactions, the centrality of effector T-helper (eTh)-dependence for activation, the role of haplotype exclusion, "nonclassical" MHC-elements, alloreactivity versus xenoreactivity, etc. Further, a set of observations believed to support the Standard Model are reinterpreted.A previous paper (Cohn, 2005c) detailed a new model (referred to as the Tritope Model) of the T-cell antigen-receptor (TCR) and analyzed its effectiveness in dealing with three basic phenomena, restrictive recognition, positive selection and allorecognition. The reasons for developing a model competing with the Standard Model have been discussed (Cohn, 2003;Cohn, 2004a;Cohn, 2004b;Cohn, 2006a;Langman and Cohn, 1999). Here we will extend the analysis of the Tritope Model by considering a set of phenomena related to the genetics, ontogeny and evolution of the TCR-MHC system. Further, the steps in the Self (S)-Nonself (NS) discrimination that are affected by the Tritope Model will be analyzed. Recalling the Tritope Model (Cohn, 2005c)The TCR encodes two distinctly different repertoires. One is germline-selected to recognize the allele-specific determinants (a) on the MHC-encoded restricting elements (R) of the species; the other is a somatically generated random repertoire that recognizes peptide (P) bound to the restricting element (R) as [PR].In order to map the two repertoires onto the TCR structure it was argued that (see List of Abbreviations):1. Single V-gene segments, Vα or Vβ, encode recognition of the allele-specific determinants (a). 2.Each domain (RI) or subunit (RII) of the R-element expresses an allele-specific determinant (a) (i.e., 2a per R).3. Peptide (P) is recognized by an anti-P site on the TCR formed by complementation of the CDR3 junctional regions of the α and β subunits.

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“…The high polymorphism in this region can be attributed to strong selection pressure as humans moved to different parts of the world and encountered new infections, leading to diversity in MHC genes through mutation and gene duplication and conversion (4-6). A population with diverse alleles of HLA classes I and II leads to herd resistance to infection and a survival advantage (7, 8). …”

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confidence: 99%

HLA Class II Molecules Influence Susceptibility versus Protection in Inflammatory Diseases by Determining the Cytokine Profile

Mangalam

Taneja

David

2013

The Journal of Immunology

111

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The MHC in humans encodes the most polymorphic genes, the HLA genes, which are critical for the immune system to clear infection. This can be attributed to strong selection pressure as populations moved to different parts of the world and encountered new kinds of infections, leading to new HLA class II alleles. HLA genes also have the highest relative risk for autoimmune diseases. Three haplotypes—HLA-DR2DQ6, DR4DQ8, and DR3DQ2—account for HLA association with most autoimmune diseases. We hypothesize that these haplotypes, along with their multiple subtypes, have survived bottlenecks of infectious episodes in human history because of their ability to present pathogenic peptides to activate T cells that secrete cytokines to clear infections. Unfortunately, they also present self-peptides/mimics to activate autoreactive T cells secreting proinflammatory cytokines that cause autoimmune diseases.

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A Genetic Herd‐Immunity Model for the Maintenance of MHC Polymorphism

Cited by 74 publications

References 57 publications

Spatial Distribution and Interspecific Associations of Tree Species in a Tropical Seasonal Rain Forest of China

Spatial Distribution and Interspecific Associations of Tree Species in a Tropical Seasonal Rain Forest of China

The Tritope Model for restrictive recognition of antigen by T-cells

HLA Class II Molecules Influence Susceptibility versus Protection in Inflammatory Diseases by Determining the Cytokine Profile

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