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W pracy przedstawiono nowe dane wskazujące na skład mikrobiomu przewodu pokarmowego człowieka, składający się z bakterii, archeonów, wirusów (w tym bakteriofagów), a także organizmów eukariotycznych i heterotroficznych jakimi są grzyby – których bytowanie w przewodzie pokarmowym określane jest mianem mykobiomu. Przewód pokarmowy człowieka podzielony na jamę ustną, gardło, przełyk, żołądek, jelito cienkie i grube, zasiedlany wyżej wymienionymi drobnoustrojami, tworzy swoisty jakościowo-ilościowy, bogaty i zróżnicowany swoisty ekosystem. Dzięki stosowaniu metod bioinformatycznych, molekularnych oraz dzięki sekwencjonowaniu metagenomowemu jest on nadal poznawany, a dzięki tym metodom możliwe jest jego lepsze poznanie. W niniejszej pracy scharakteryzowano grupy systematyczne bakterii, archeonów, wirusów i grzybów występujące w poszczególnych odcinkach przewodu pokarmowego i wskazano także na enterotypy jelita grubego. Analizując wymienione grupy mikroorganizmów w poszczególnych odcinkach przewodu pokarmowego człowieka, należy zauważyć, że odcinek jelita grubego i jamy ustnej jest „wyposażony” w najbardziej bogaty mikrobiom, natomiast gardło i przełyk posiada najmniejszą liczbę drobnoustrojów wchodzących w skład mikrobiomu. Wśród całości mikrobiomu przewodu pokarmowego człowieka najliczniejszą grupę stanowią bakterie usytuowane w jamie ustnej i jelicie cienkim, zaś najbardziej ograniczoną grupę bakterii rejestruje się w gardle i przełyku. Archeony natomiast zostały opisane najliczniej w jelicie grubym i jamie ustnej, a nie zostały stwierdzone w gardle i jelicie cienkim. Wymieniane w odcinkach przewodu pokarmowego wirusy, najliczniej występowały w jelicie grubym i jamie ustnej, natomiast nie stwierdzono ich w żołądku. Występujące w mikrobiomie grzyby, najobficiej stwierdzane były w jelicie grubym i żołądku, a w najmniejszej ilości w gardle i jelicie cienkim.

Cathelicidins are Important immunological peptides – HDPs (Host Defense Peptides) with high biological activity in mammals, including human and vertebrate animals. These evolutionary ancient molecules in these organisms are natural elements of antimicrobial, antiviral, antifungal and antiparasitic immunity against which germs and parasites have not developed immunity, which makes them alternatives to antibiotics. Catelicidins in human and vertebrates affect the germs and parasites directly and indirectly by activating the immune system.

Influenza viruses are a significant cause of respiratory infections, causing 3-5 million clinical infections and 250-500 thousand deaths per year. Infections caused by the influenza virus induce a host immune response at the non-specific and specific level (defined as natural and acquired), which leads to limitation of virus replication. Moreover the elements of immunological memory are induced so that they can protect against subsequent infection by the influenza virus. However, there is still no effective way for the total elimination of this virus, and the only effective method to combat this pathogen appears to be vaccination, which through immune system activation greatly limits its spread. The present paper presents the immune reaction at different levels in response to the influenza virus after entering the body and the mechanisms of the influenza virus for avoiding reactions of the immune system, which correspond to its high variability at the molecular level. Moreover, in this paper we describe various methods of stimulating the organism's immune systems with different generations of vaccines and their effectiveness in the fight against this pathogen.

Innate lymphoid cells (ILC) is a newly described family of immune cells that are part of the natural immunity which is important not only during infections caused by microorganisms, but also in the formation of lymphoid tissue, tissue remodeling after damage due to injury and homeostasis tissue stromal cells. Family ILC cells form NK cells (natural killer) and lymphoid tissue inducer T cells (LTi), which, although they have different functions, are evolutionarily related. NK cells are producing mainly IFN-γ, whereas LTi cells as NKR+LTi like, IL-17 and/or IL-22, which suggests that the last two cells, can also represent the innate versions of helper T cell--TH17 and TH22. Third population of ILC is formed by cells with characteristics such as NK cells and LTi (ILC22)--which are named NK22 cells, natural cytotoxicity receptor 22 (NCR22) cells or NK receptor-positive (LTi NKR+) LTi cells. Fourth population of ILC cells are ILC17--producing IL-17, while the fifth is formed by natural helper type 2 T cells (nTH2), nuocyte, innate type 2 helper cells (IH2) and multi-potent progenitor type 2 cells (MPPtype2). Cells of the last population synthesize IL-5 and IL-13. It is assumed that an extraordinary functional diversity of ILC family, resembles T cells, probably because they are under the control of the corresponding transcription factors - as direct regulation factors, such as the family of lymphocytes T.

The study of the immune system started about a hundred years ago with the phagocytosis experiments of Mechnikov. That which is now referred to as non-specific cell-mediated immunity was quickly linked to studies related to, inter alia, the immunity determined by antibodies (humoral), which has long been considered as the first line of defense against diseases caused by micro-organisms, including viruses. Despite their small size, viruses have a huge impact on the host, as they produce substances that stimulate the antiviral response and affect it. The paper presents selected data on participation of immune system cells and their receptors in viral infections, as the host cells have evolved a number of specific cellular and humoral components of the signaling networks that are involved in the detection and the host's response to viral infections.

The paper describes the characteristics, receptor profile and functions of T lymphocyte subpopulations (helper, cytotoxic, regulatory, memory and others). Among T helper cells one can enumerate Th0, Th1, Th2, Th9, Th17, Th22, T(FH) and nTh2, while T cytotoxic cells include Tc, NKT, Tγδ, and T CD8αα (IEL). Among regulatory cells there are nTreg, iTreg, T(R)1, and iT(R)35, as well as T lymphocytes with CD8, such as CD8+CD122+, CD8+CD28-, and CD11c+CD8+. And among memory T cells there are Tcm and Tem. Moreover, there are some so-called other T cells, such as Tn (T αβ CD4+ and T αβ CD8+), T exhausted and T anergic.

Neutrophils are one of the first cells of the immune system recruited to the site of infection, representing the host's most effective and numerous front-line defenders. Recently, a novel antimicrobial mechanism of neutrophils has been described: upon activation, they release DNA and a subset of their granule content, forming neutrophil extracellular traps (NETs). These extracellular, chromatin structures, which contain histones and neutrophil granule proteins, can trap and kill a broad spectrum of microbes, including Gram-positive and Gram-negative bacteria, fungi, protozoa and viruses. Some of the pathogens, which are trapped and exposed to high local concentrations of antimicrobial compounds, employ strategies against NET binding, including surface modification and/or degradation of NET by DNases. It has been suggested that NETs are formed during active cell death, recently named NETosis. New data indicate that this novel mechanism of cell death requires interaction between three processes--reactive oxygen species generation, histone citrullination and autophagy--and significantly differs from previously known types of cell death, including apoptosis and necrosis. Moreover, the release of nuclear chromatin was also described for other types of cells--mast cells and eosinophils. Mast cells, like neutrophils, under certain conditions release nuclear chromatin and may undergo a similar active cell death program, while eosinophils release only mitochondrial chromatin, and its release does not lead to the death of these cells.