Kappa deleting recombination excision circle (KREC) is a molecular structure that occurs as a result of the specific response of B lymphocytes to protect the immune system against a wide variety of antigens and is considered to be an indicator of early immune response, especially in immunodeficiency disease patients. KREC can be measured with molecular analysis methods to show B cell output from the bone marrow and there has been an increase in clinical studies on the subject recently. This review is focused on explaining the mechanism of KREC occurrence, the importance of KREC measurement and its role in the treatment of diseases.

The continuing pandemic of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was emerged in China, and has spread rapidly all over the whole world. Thousands of cases and deaths reported each day and it is an exceptional situation in which emergency response is required for many patients. While COVID-19 cases are seen in all age groups, death rates are high in cases of cancer that cause immunodeficiency, especially in elderly people with impaired immune systems, in those with chronic diseases.
The interaction between infections and the immune system is clear and there is a lot of relevant literature information. By keeping the immune system strong, infections can be overcome with less damage, and the harmful effects of inflammation and death rates can be reduced. Vitamins A, C and D are effective in the active functioning of the immune system, and their deficiencies have many adverse conditions, particularly susceptibility to infections. Although there is no specific treatment method, antiviral drug or vaccine with proven reliability for the treatment of COVID-19, the drugs recommended by the World Health Organization are being used. The effectiveness and efficiency of these drugs are controversial. In addition to these drugs, alternative treatment approaches are needed. In this literature review, the importance of vitamins A, C and D on the pathophysiology of SARS-CoV-2 and on the early-stage administration of high-dose intravenous (IV) C, oral A and D vitamins, which are alternative approaches, in the treatment of COVID-19 is shared

Objective: There are limited studies about NK cells that may have an immunoregulatory role in Behçet’s Disease. NK cell receptor, perforin and granzyme mRNA expressions were analyzed in both active and inactive BD patients.
Materials and Methods: NKp30, NKp46, NKG2D, perforin and granzyme mRNA expression were analyzed in 42 patients with Behçet’s disease and 14 controls by RT-PCR. CD3+ T, and NK cell subsets were analyzed by flow cytometry.
Results: NKp30, NKp46, NKG2D, perforin and granzyme expression levels between patients and healthy subjects did not show any significant differences. However, a positive correlation was detected between CD3-CD16+ CD56dim NK cell frequencies and NKG2D and NKp46 mRNA levels in active BD patients and between CD3+ T cell frequencies and NKp46 mRNA levels in inactive Behçet’s patients.
Conclusion: Although, a significant difference does not exist between NKp30, NKp46, NKG2D, perforin and granzyme mRNA expressions, further functional studies are necessary to rule out the potential role of these molecules in the pathogenesis of Behçet’s Disease.

Objective: Natural killer cells play immunomodulatory role the pathogenesis of chronic inflammatory airway diseases. NK cells may induce allergic airway inflammation by increasing the production of type 2 cytokines.
Materials and Methods: We measured intracytoplasmic cytokine levels of IL-13, IL-4, IFNγ and IL-10 in NK cells and serum levels of IFN-γ, TNF-α, IL-2, IL-8, IL-4, IL-5, IL-6, IL-17, IL12, IL-13, IL-1β and IL-10 in patients with newly diagnosed asthma, asthmatic patients under treatment (UT) and controls by using flow cytometry and ProcartaPlex multiplex immunoassays kit.
Result: IFN-γ+NK1 cells were decreased in both patient groups; comparing both asthmatic groups, IFN-γ+NK1 cells were higher in asthmatics UT. Intracellular IL-4 of NK cells were higher in both patient groups vs. controls. IL-10+NK cells were lower in both patient groups vs. controls. We detected increased numbers of IL-13+NK2 cells in newly-diagnosed asthmatics vs. asthmatics UT and controls.
In serum we found elevated levels of IL-1β in newly-diagnosed asthmatics vs. asthmatics UT Newly-diagnosed asthmatics showed higher IL-8 levels compared to asthmatics UT and controls. We showed higher IL-5 levels in newly-diagnosed asthmatics vs. controls. Higher IL-13 levels were detected in newly-diagnosed asthmatics vs. other groups and also in controls vs. patients with asthma UT. IL-10 and IL-12 levels were decreased in newly-diagnosed asthmatics vs. controls. IL-2 levels were low in both asthmatics vs. controls.
Conclusion: In order to use NK cells as a therapeutic target, a strategy must be established to regulate its cytokine secretion functions with respect to their role of these cells in each disease.

Objective: In our study, it was aimed to investigate the presence of peptides of the 13 amino acids-long non-structural protein 11 (Nsp11) of SARS-CoV-2 that may be associated with the higher risk of autoimmune reactions in individuals with certain HLA serotypes.
Materials and Methods: For this purpose, the binding affinities of Nsp11-derived peptides to 12 major histocompatibility complex (MHC) supertype representative human leukocyte antigen (HLA) alleles were predicted by NetMHCcons and NetCTLpan. Strongly binding or predicted epitope peptides were sought in human proteome by blastp. Whether the sequence containing the overlapping peptide had a strong binding affinity to the same HLA allele as the Nsp11 peptide was also checked.
Results: One of the Nsp11-derived peptides was predicted to be strongly bound to the HLA-B*15: 01 allele and the other to be the cytotoxic T lymphocyte (CTL) epitope that binds to the HLA-A*01: 01 allele. Alignment result with immunoglobulin heavy chain junction region (MOP92462.1) appeared on top within the blastp search results for peptides. A peptide of the sequence containing the overlapping peptide was predicted to be the CTL epitope that binds to the HLA-B*15: 01 allele.
Conclusion: The results indicate that individuals with the HLA-B*15: 01 allele may have a risk of autoimmune reactions from SARS-CoV-2 infection