Antibody repertoires in infants and adults: effects of T-independent and T-dependent immunizations

Abstract

Polysaccharide(PS)-encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis are among the most prevalent bacterial pathogens of humans. Infections caused by these organisms are both common (otitis media, sinusitis) and severe (meningitis, bacteremia). Antibodies directed against the capsular PS of encapsulated bacteria prevent infection by promoting opsonophagocytic killing. Most bacterial PS, however, are type II T-cell-independent (TI-2) antigens that are poorly immunogenic in young children at highest risk of developing disease. Conjugation of bacterial PS to a protein carrier converts the immune response to a T-cell-dependent (TD) form and significantly improves the immunogenicity of PS, especially in infants. H. influenzae type b (Hib) is a major cause of invasive infection in non-immune children. The medical importance of this pathogen and the availability of both TI-2 and TD Hib PS vaccine formulations have made the human anti-Hib-PS immune response an excellent model for the study of the biology of these B cell responses.

Immunization withPorphyromonas gingivalisCapsular Polysaccharide PreventsP. gingivalis-Elicited Oral Bone Loss in a Murine Model

“…When the IgG response to bacterial capsules is present, IgG2 usually predominates (33), and these antibodies are relatively poor opsonins that weakly activate the complement cascade. To enhance the host antibody response and to switch the IgG subtype response to these antigens, CPSs have been conjugated to carrier molecules (1,14). Previously, Choi et al (6) reported that a P.…”

The mechanism of humoral immune response to allogeneic organ transplantation

“…К тимус-зависимым относятся антигены, ко-торые не могут напрямую при взаимодействии с ВкР активировать В-клетки, но способны опосре-дованно, при участии Т-хелперов индуцировать активацию В-клеток, будучи процессированными и презентированными АПК в комплексе с молеку-лой МНС [14][15][16]. Очевидно, что к данной группе антигенов относятся все белковые структуры, в том числе HLA-молекулы, представляющие собой гликопротеины.…”

The role of complement in the success of vaccination with conjugated vs. unconjugated polysaccharide antigen

“…Development of the marginal zone is delayed in mouse (up to 3-4 weeks) and human (up to two years, but it becomes visible as of 4 months) and encompasses maturation and organisation of marginal zone B-cells (expressing CR1, CR2, CD1d) [76] as well as population with memory B-cells [77,78]. This is the basis for the impairment in the immune response of the young in both, human and mouse, but it can be overcome by conjugation of polysaccharide vaccines [79,80]. In the elderly, by contrast, unconjugated polysaccharides and protein-conjugated oligosaccharides prove equally efficacious [81,82], at least in the absence of functional hyposplenism [83].…”