MIIM20002 Lecture Notes - Lecture 18: Macrophage, Adaptive Immune System, Keratin
28 Jul 2018
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Document Summary
Streptococcus pneumoniae induces the formation of pus. An extracellular bacterium that evades phagocyte action, thus is. Classic appearance of a gram stain of sputum from a patient pneumococcal pneumonia. The smear shows lancet-shaped diplococci with gram stain of s. pneumoniae in sputum. Neutrophils produce webs of dna called extracellular traps (nets) containing granules of the neutrophils. Several cell wall adhesins documented for nasopharyngal mucosa and lung mucosa (pneumocytes) including: Can develop antibodies to these more conserved antigens. Coats cell wall structures, resulting in reduced opsonisation and delayed phagocytosis thus the pneumococcus continues to replicate. Highly immunogenic (dominant antigenic structure) but antibodies made against the capsular antigens do not cross react, or only weakly cross react and they take time to be produced. This is why previous infection doesn"t provide immunity to other capsular serotypes. Neutrophil extracellular traps (nets): extrafibrillary meshes extruded from neutrophils (mainly. Dna) that trap microorganisms are evaded by pneumococcal dna-ases which break down.
