Odata cu inaintarea in varsta se modifica strategia de aparare imunitara a organismului. De exemplu, celulele natural killer sunt mai multe, dar cantitatea de citochine si eficienta per celula natural killer este diminuata. Practic, cresterea cantitativa este o compensare a diminuarii calitative. Si cu macrofagele se intampla cam acelasi lucru. Subtipurile de limfocite de asemenea isi schimba profilul cantitativ si calitativ. E si o veste buna, exista si imbatranire sanatoasa.
O posibila corelatie pentru raspunsul imunitar adeseori ineficient la organismele cu varsta inaintata ar putea fi scaderea treptata a cooperarii intercelulare. De exemplu, in recunoasterea antigenica a ARN ului viral SARS-CoV-2 sunt implicati receptori TLR 7 (12). Acesti receptori odata activati, induc prompt eliberarea de interferon 1. Un studiu care a investigat densitatea receptorilor TLR pe celule dendritice plasmacitoide (acestea functioneaza ca CPA care care preiau virusul din circulatie si au cea mai potenta actiune in eliberarea de interferon 1) la persoane cu varsta medie 74 de ani vs. persoane cu varsta medie 28 de ani a gasit ca prezenta de TLR 7 si TLR 9 este mult scazuta pe celulele dendritice de la seniori fata de juniori (13). Acelasi studiu sustine o reducere de peste 60%, la seniori vs juniori a proportiei de celule dendritice plasmacitoide care pot elibera IFN 1 dupa stimularea cu virus gripal. Dealtfel, in populatia americana >90% dintre pierderile de vieti anuale din cauza infectiei gripale apar la grupa de varsta de peste 64 ani (14).
Ca o mentiune, variabilitatea simptomelor dupa infectia SARS-CoV-2 e strans legata de tropismul virusului adica de celulele si organele pe care le poate infecta, de densitatea receptorilor ACE2 pe celulele respective, de imunitatea locala cat si de cea a intregului organism. Deoarece tractul respirator, digestiv, rinichiul, inima, pielea exprima receptorul ACE2, efectele imediate ale infectiei pot predomina intr-unul dintre acestea la inceput, dar aspectul constant este ca in formele grave de boala plamanul este cel mai lovit.
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