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The human major histocompatibility complex (MHC) region encodes three types of class II molecules designated HLA-DR, -DQ, and -DP. Both the HLA-DQ and -DP gene region comprise a duplicated tandem of A and B genes, whereas in macaques, only one set of genes is present per region. A substantial sequencing project on the DQ and DP genes in various macaque populations resulted in the detection of previously 304 unreported full-length alleles. Phylogenetic studies showed that humans and macaques share trans-species lineages for the DQA1 and DQB1 genes, whereas the DPA1 and DPB1 lineages in macaques appear to be species-specific. Amino acid variability plot analyses revealed that each of the four genes displays more allelic variation in macaques than is encountered in humans. Moreover, the numbers of different amino acids at certain positions in the encoded proteins are higher than in humans. This phenomenon is remarkably prominent at the contact positions of the peptide-binding sites of the deduced macaque DPβ-chains. These differences in the MHC class II DP regions of macaques and humans suggest separate evolutionary mechanisms in the generation of diversity. [ABSTRACT FROM AUTHOR]

Virus-specific cytotoxic T lymphocytes (CTLs) are major effectors in acquired immune responses against viral infection. Virus-specific CTLs recognize specific viral peptides presented by major histocompatibility complex-class I (MHC-I) on the surface of virus-infected target cells via their T cell receptor and eliminate target cells by both direct and indirect mechanisms. In human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections, host immune responses fail to contain the virus and allow persistent viral replication, leading to AIDS progression. CTL responses exert strong suppressive pressure on HIV/SIV replication and cumulative studies have indicated association of HLA/MHC-I genotypes with rapid or slow AIDS progression.

Palynological analyses were carried out on twenty six (26) samples obtained from exposures of Mamu Formation in the Enugu area and two other reference locations to the south of Enugu (Mamu/Ajali transition exposed at Umulolo and part of the Mamu Formation exposed at Leru). Sixty three (63) species of pollens, twenty three (23) species of spores and some dinoflagellates (16 species) and foraminiferal test linings were recovered. The main maastrichtian diagnostic species of pollen and spores include Buttinia andreevi, Cingulasporites omatus, Echitrisporites triaguliformis, Ephedripites ambonoides, Macrotyloma brevicaule, Retidiporites magdalensis, Syncolporites marginatus, Zonosulcites parvus, Constructipollenites ineffectus and Auriculiidites reticulates. Among the dinoflagellates two are diagnostic. They are Andalusiella mauthei, Lejeunecysta sp. Sedimentary structures observed include symmetrical ripples, widespread burrows by trace fossils such as Ophiomorpha and Skolithos. The recovery of greater than 70% of continental palynomorphs shows that the depositional environment of Mamu Formation is probably continental with minor marine incursions. It is probably a Barrier Island setting with occasional transgressive phases resulting in the observed parallic sequences. [ABSTRACT FROM AUTHOR]