Clinical diagnosis
Case 226
【Discussion】
There are several lumens in human where pathogens come into our body. Oral cavity, nasal cavity, bronchial lumen and digestive lumen are representative. These lumens have their own defense system against pathogens: virus, bacillus and parasites. Tonsil, nose associated lymphoid tissue (NALT), bronchus associated lymphoid tissue (BALT), mucosa associated lymphoid tissue (MALT) are listed. Macrophage and dendritic cells are habitants in this defense system. They phagocyte pathogens and transmit the information of their antigen to helper T lymphocytes. T cells transmit the antigen information which is obtained from dendritic cells, to naïve B cells. Naïve B cells transform to plasma cells, producing Ig A, Ig M and Ig G. The percentage of Ig A , Ig M and Ig G of the immune-globulins in whole blood is 15%, less than 10% and approximately 75%, respectively (1). Ig A is secreted to the surface of these lumens with mucin produced by goblet cells.
When COVID19 viruses (SARS-CoV2) try to invade to nasal and bronchial epithelium, they meet cilia and mucin containing Ig A. It is well known for not only SARS-CoV2 but also SARS (severe acute respiratory syndrome) and MERS (middle east respiratory syndrome) to least infect the youth, children or infants. Although PCR is positive, they are in condition of no symptom or feeling the loss sensation of taste and olfactory. There are four corona viruses infected to human. Those infections commonly occur in infants and their percentage is almost 100% before the age of six. Then, most human gain immunity for human corona viruses. Corona virus is RNA virus with an envelope equipped with spikes for triggering cell membrane of host. There is a theory of cross immunity which means immunity gained by one virus works to another virus. SARS-CoV2 virus is reported to arise from collection from bat living in the south China in 2013 (2) and transformed with the ability to infect to human in 2019. The percentage which the gene of SARS-CoV2 matches to the collection virus from bat was reported to 96% (2). When viruses causing COVID19 (SARS-CoV2) enter the lumen of nose or bronchial tract, it is exposed to cilia, mucin and IgA. The IgA produced by human corona virus has the potential to work against COVID19 from a view point of cross immunity. SAR-CoV2 avoid this defense system and hide into nerve of taste and olfactory. It induces abnormal sensation of taste and olfactory.
From the end of 2020 to the beginning of 2021, COVID19 is still transforming, leading to easily infect to human, and acutely increasing the number of patient with COVID19. This implies the ability to break through the first defense line strengthens. Influenza has more potency to break through the first defense line than corona virus. Youth, children and infants are susceptible to infect influenza with ease as well as the elder. It is unclear now and requires time whether SAR-CoV2 will become human corona virus or like a seasonal influenza in future.
【Summary】
We present an eighty years-old female with COVID19. Chest CT 4 days after infection showed no evidence of abnormality in pulmonary area. It is borne in mind that when COVID19 viruses (SARS-CoV2) try to invade to nasal and bronchial epithelium, they meet cilia and mucin containing Ig A. The percentage of Ig A , Ig M and Ig G of the immune-globulins in whole blood is 15%, less than 10% and approximately 75%, respectively. Not only SAR-CoV2 but also SARS (severe acute respiratory syndrome) SAR-CoV2 and MERS (middle east respiratory syndrome) SAR-CoV2 least infect the youth, children or infants. The IgA produced by human corona virus has the potential to work against SAR-CoV2 virus as cross immunity. SAR-CoV2 avoid mucin containing IgA specific to human corona virus and hide into nerves of taste and olfactory. Then, some of them feel loss of sensation of taste and olfactory.
【References】
1.Morton HC,van Egmond M and van de Winkel JG.(1997)"Structure and function of human IgA Fc receptors (Fc alpha R).". Crit.Rev.Immunol.16,423–40.
2.GLEN OWEN POLITICAL EDITOR FOR THE MAIL ON SUNDAY. Wuhan lab was performing coronavirus experiments on bats from the caves where the disease is believed to have originated - with a £3m grant from the US. Wuhan lab was performing experiments on bats from coronavirus caves Daily Mail Online
3.Ackermann M, et al. Pulmonary Vascular Endothelialitis, Thrombosis, and Angiogenesis in Covid-19. N Engl J Med. 2020 May 21.
2021.3.31