Active natural acquired immunity
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Understanding Active Natural Acquired Immunity
Introduction to Active Natural Acquired Immunity
Active natural acquired immunity refers to the resistance against specific pathogens developed by an organism through natural exposure to antigens. This type of immunity involves the stimulation of specialized lymphocytes and the production of antibodies in response to the antigens encountered during infections . This immune response can be lifelong for some diseases, while for others, it may be short-lived.
Natural Acquired Immunity to Human Papillomavirus (HPV)
Research indicates that naturally acquired antibodies against HPV can provide modest protection against subsequent infections, particularly in females. A systematic review and meta-analysis involving over 24,000 individuals from 18 countries found significant protection against subsequent HPV-16 and HPV-18 infections in females, but not in males . This suggests that natural immunity to HPV is more effective in females, potentially due to differences in immune response mechanisms between genders.
Naturally Acquired Immunity to Malaria
Plasmodium falciparum
Naturally acquired immunity to Plasmodium falciparum, the parasite responsible for the most severe form of malaria, evolves with age and repeated exposure. Studies have shown that children in malaria-endemic areas develop humoral immunity over time, characterized by specific antibody profiles that help control parasitemia and fever . This immunity is associated with higher levels of specific antibodies, such as MSP1-specific IgG3 and IgA, which are crucial for protection against malaria .
Plasmodium vivax
Individuals acquire immunity to Plasmodium vivax more quickly than to Plasmodium falciparum, regardless of transmission intensity. This rapid acquisition of immunity involves both humoral and cellular responses targeting various antigens, including merozoite surface proteins and circumsporozoite proteins . The presence of naturally acquired transmission-blocking immunity in several populations supports the potential for developing effective vaccines against P. vivax.
Naturally Acquired Immunity to Streptococcus pneumoniae
Streptococcus pneumoniae, a major cause of pneumonia, septicaemia, and meningitis, induces naturally acquired immunity through nasopharyngeal colonization. This colonization triggers antibody responses to protein and capsular antigens and Th17 CD4+ cellular immune responses, which are protective against subsequent infections . The combination of antibody and Th17 cell responses is essential for protection against pneumonia, while antibodies alone are crucial for preventing sepsis.
Naturally Acquired Immunity to Hepatitis E Virus (HEV)
Both naturally acquired and vaccine-induced immunity can protect against HEV infection. A study involving 12,409 participants found that pre-existing immunity and vaccine-induced immunity significantly reduced the risk of HEV infection . Additionally, naturally acquired anti-HEV IgG levels decrease steadily over time, but vaccination can induce long-lasting, high-level anti-HEV IgG concentrations .
Conclusion
Active natural acquired immunity plays a crucial role in protecting against various pathogens, including HPV, malaria, Streptococcus pneumoniae, and HEV. The effectiveness and duration of this immunity can vary depending on the pathogen and the individual's immune response. Understanding these mechanisms is essential for developing effective vaccines and therapeutic strategies to enhance immunity and prevent infections.
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