Criteria for the clinically defined diagnosis of lymphocyte-variant hypereosinophilia have not been strictly set forth. Diagnosis must first rule out other causes of eosinophilia and hypereosinophilia, such as those due to allergies, drug reactions, infestations, and autoimmune diseases as well as those associated with eosinophilic leukemia, clonal eosinophilia, systemic mastocytosis, and other malignancies (see causes of eosinophilia). Criteria for the diagnosis include findings of: a) long term hypereosinophila (i.e. eosinophil blood counts >1,500/microliter) plus physical findings and symptoms associated with the disease; b) bone marrow analysis showing abnormally high levels of eosinophils; c) elevated serum levels of Immunoglobulin E, other immunoglobulins, and CCL17; d) eosinophil infiltrates in afflicted tissues; e) increased numbers of blood and/or bone marrow T cells bearing abnormal immunophenotype cluster of differentiation markers as defined by fluorescence-activated cell sorting (see above section on Pathogenesis); f) abnormal T cell receptor arrangements as defined by polymerase chain reaction methods (see above section on Pathogenesis); and g) evidence of excessive IL-5 secretion by lymphocytes (see above section on Pathogenesis). In many clinical settings, however, studies on the T cell receptor and IL-5 are not available and therefore not routine parts of the diagnostic work-up or criteria for the disease. The finding of T cells bearing abnormal immunophenotype cluster of differentiation markers is critical to making the diagnosis.

Treatments used to combat autoimmune diseases and conditions caused by eosinophils include:

- corticosteroids – promote apoptosis. Numbers of eosinophils in blood are rapidly reduced

- monoclonal antibody therapy – e.g., mepolizumab or reslizumab against IL-5, prevents eosinophilopoiesis

- antagonists of leukotriene synthesis or receptors

- imatinib (STI571) – inhibits PDGF-BB in hypereosinophilic leukemia

Monoclonal antibodies such as dupilumab and lebrikizumab target IL-13 and its receptor, which reduces eosinophilic inflammation in pateints with asthma due to lowering the number of adhesion molecules present for eosinophils to bind to, thereby decreasing inflammation. Mepolizumab and benralizumab are other treatment options that target the alpha subunit of the IL-5 receptor, thereby inhibiting its function and reducing the number of developing eosinophils as well as the number of eosinophils leading to inflammation through antibody-dependent cell-mediated cytotoxicity and eosinophilic apoptosis.

Lymphocyte-variant hypereosinophilia usually takes a benign and indolent course. Long term treatment with corticosteroids lowers blood eosinophil levels as well as suppresses and prevents complications of the disease in >80% of cases. However, signs and symptoms of the disease recur in virtually all cases if corticosteroid dosages are tapered in order to reduce the many adverse side effects of corticosteroids. Alternate treatments used to treat corticosteroid resistant disease or for use as corticosteroid-sparing substitutes include interferon-α or its analog, Peginterferon alfa-2a, Mepolizumab (an antibody directed against IL-5), Ciclosporin (an Immunosuppressive drug), imatinib (an inhibitor of tyrosine kinases; numerous tyrosine kinase cell signaling proteins are responsible for the growth and proliferation of eosinophils {see clonal eosinophilia}), methotrexate and Hydroxycarbamide (both are chemotherapy and immunosuppressant drugs), and Alemtuzumab (a antibody that binds to the CD52 antigen on mature lymphocytes thereby marking them for destruction by the body). The few patients who have been treated with these alternate drugs have exhibited good responses in the majority of instances. Reslizumab, a newly developed antibody directed against interleukin 5 that has been successfully used to treat 4 patients with the hypereosinophilic syndrome, may also be of use for lymphocyte-variant eosinophilia. Patients suffering minimal or no disease complications have gone untreated.

In 10% to 25% of patients, mostly 3 to 10 years after initical diagnosis, the indolent course of lymphocyte-variant hypereosinophilia changes. Patients exhibit rapid increases in lymphadenopathy, spleen size, and blood cell numbers, some cells of which take on the appearance of immature and/or malignant cells. Their disease soon thereafter escalates to an angioimmunoblastic T-cell lymphoma, peripheral T cell lymphoma, Anaplastic large-cell lymphoma (which unlike most lymphomas of this type is Anaplastic lymphoma kinase-negative), or Cutaneous T cell lymphoma. The malignantly transformed disease is aggressive and has a poor prognosis. Recommended treatment includes chemotherapy with Fludarabine, Cladribine, or the CHOP combination of drugs followed by bone marrow transplantation.

Although frequently employed to treat patients experiencing the cytokine storm associated with ARDS, corticosteroids and NSAIDs have been evaluated in clinical trials and have shown no effect on lung mechanics, gas exchange, or beneficial outcome in early established ARDS.

Preliminary data from clinical trials involving patients with sepsis-induced ARDS have shown a reduction in organ damage and a trend toward improvement in survival (survival in ARDS is approximately 60%) after administering or upregulating a variety of free radical scavengers (antioxidants).

In a large number of phase I and phase II studies, autologous and allogeneic CIK cells displayed a high cytotoxic potential against a broad range of varying tumor entities, whereas side effects were only minor. In many cases, CIK cell treatment led to complete remissions of tumor burden, prolonged survival durations and improved quality of life, even in advanced disease stages.

Currently, the utilization of CIK cell treatment is restricted to clinical studies, but this therapeutic approach might also benefit patients as first-line treatment modality in the future.

The international registry on CIK cells (IRCC) was founded in 2011 as an independent organization, dedicated to collect data about clinical trials utilizing CIK cells and subsequent analysis to determine the latest state of clinical CIK cell research. A particular focus is thereby the evaluation of CIK cell efficacy in clinical trials and side effects.

Gleich's syndrome, which may be a form of lymphocyte-variant hypereosinophilia, involves hypereosinophilia, elevated blood levels of IgM antibodies, and clonal expansion of T cells. Similar to lymphocyte=variant hypereosinophilia, the increased levels of blood eosinophils in Gleich's syndrome is thought to be secondary to the secretion of eosinophil-stimulating cytokines by a T cell clone(s).

The regulatory T cells (Tregs ), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune disease. Tregs are immunosuppressive and generally suppress or downregulate induction and proliferation of effector T cells. Tregs express the biomarkers CD4, FOXP3, and CD25 and are thought to be derived from the same lineage as naïve CD4 cells. Because effector T cells also express CD4 and CD25, Tregs are very difficult to effectively discern from effector CD4+, making them difficult to study. Recent research has found that the cytokine TGFβ is essential for Tregs to differentiate from naïve CD4+ cells and is important in maintaining Treg homeostasis.

Mouse models have suggested that modulation of Tregs can treat autoimmune disease and cancer and can facilitate organ transplantation. Their implications for cancer are complicated. Tregs tend to be upregulated in individuals with cancer, and they seem to be recruited to the site of many tumors. Studies in both humans and animal models have implicated that high numbers of Tregs in the tumor microenvironment is indicative of a poor prognosis, and Tregs are thought to suppress tumor immunity, thus hindering the body's innate ability to control the growth of cancerous cells. Recent immunotherapy research is studying how regulation of T cells could possibly be utilized in the treatment of cancer.

This type of GvHD is associated with transfusion of un-irradiated blood to immunocompromised recipients. It can also occur in situations in which the blood donor is homozygous and the recipient is heterozygous for an HLA haplotype. It is associated with higher mortality (80-90%) due to involvement of bone marrow lymphoid tissue, however the clinical manifestations are similar to GVHD resulting from bone marrow transplantation. Transfusion-associated GvHD is rare in modern medicine. It is almost entirely preventable by controlled irradiation of blood products to inactivate the white blood cells (including lymphocytes) within.

A "monocyte count" is part of a complete blood count and is expressed either as a percentage of monocytes among all white blood cells or as absolute numbers. Both may be useful but these cells became valid diagnostic tools only when monocyte subsets are determined.

Monocytosis is the state of excess monocytes in the peripheral blood. It may be indicative of various disease states.

Examples of processes that can increase a monocyte count include:

- chronic inflammation

- stress response

- Cushing's syndrome (hyperadrenocorticism)

- immune-mediated disease

- granulomatous disease

- atherosclerosis

- necrosis

- red blood cell regeneration

- viral fever

- sarcoidosis

A high count of CD14+CD16++ monocytes is found in severe infection (sepsis)

In the field of atherosclerosis high numbers of the CD14++CD16+ intermediate monocytes were shown to be predictive of cardiovascular events in at risk populations.

There are a large number of clinical trials either ongoing or recently completed in the investigation of graft-versus-host disease treatment and prevention. Currently, there are no reliable molecular markers reflecting the onset or clinical course of aGVHD. However, it has been shown that genes responsible for cytokine signaling, inflammatory response, and regulation of cell cycle are differentially expressed in patinets with fatal GvHD versus „indolent“ GvHD.

On May 17, 2012, Osiris Therapeutics announced that Canadian health regulators approved Prochymal, its drug for acute graft-versus host disease in children who have failed to respond to steroid treatment. Prochymal is the first stem cell drug to be approved for a systemic disease.

In January 2016, Mesoblast released results of a Phase2 clinical trial on 241 children with acute Graft-versus-host disease, that was not responsive to steroids. The trial was of a mesenchymal stem cell therapy known as remestemcel-L or MSC-100-IV. Survival rate was 82% (vs 39% of controls) for those who showed some improvement after 1 month, and in the long term 72% (vs 18% of controls) for those that showed little effect after 1 month.

An increase in eosinophils, i.e., the presence of more than 500 eosinophils/microlitre of blood is called an eosinophilia, and is typically seen in people with a parasitic infestation of the intestines; autoimmune and collagen vascular disease (such as rheumatoid arthritis) and Systemic lupus erythematosus; malignant diseases such as eosinophilic leukemia, clonal hypereosinophilia, and Hodgkin's disease; lymphocyte-variant hypereosinophilia; extensive skin diseases (such as exfoliative dermatitis); Addison's disease and other causes of low corticosteroid production (corticosteroids suppress blood eosinophil levels); reflux esophagitis (in which eosinophils will be found in the squamous epithelium of the esophagus) and eosinophilic esophagitis; and with the use of certain drugs such as penicillin. But, perhaps the most common cause for eosinophilia is an allergic condition such as asthma. In 1989, contaminated L-tryptophan supplements caused a deadly form of eosinophilia known as eosinophilia-myalgia syndrome, which was reminiscent of the Toxic Oil Syndrome in Spain in 1981.

Eosinophils play an important role in asthma as the number of accumulated eosinophils corresponds to the severity of asthmatic reaction. Eosinophilia in mice models are shown to be associated with high interleukin-5 levels. Furthermore, mucosal bronchial biopsies conducted on patients with diseases such as asthma have been found to have higher levels of interleukin-5 leading to higher levels of eosinophils. The infiltration of eosinophils at these high concentrations causes an inflammatory reaction. This ultimately leads to airway remodelling and difficulty of breathing.

Eosinophils can also cause tissue damage in the lungs of asthmatic patients. High concentrations of eosinophil major basic protein and eosinophil-derived neurotoxin that approach cytotoxic levels are observed at degranulation sites in the lungs as well as in the asthmatic sputum.

Natural killer T (NKT) cells are a heterogeneous group of T cells that share properties of both T cells and natural killer cells. Many of these cells recognize the non-polymorphic CD1d molecule, an antigen-presenting molecule that binds self and foreign lipids and glycolipids. They constitute only approximately 0.1% of all blood T cells. Natural killer T cells should not be confused with natural killer cells.

IgG4-related disease or Immunoglobulin G4-related disease is a condition dacryoadenitis, sialadenitis, lymphadentitis, and pancreatitis (i.e. inflammation of the lacrimal glands, salivary glands, lymph nodes, and pancreas, respectively) plus retroperitoneal fibrosis. Less commonly, almost any other organ or tissue except joints and brain may be beleaguered by the inflammatory disorder. About 1/3 of cases exhibit eosinophilia or, rarely, hypereosinophilia. This increase in blood eosinophil count is often associated with abnormal T-lymphocyte clones (e.g increased numbers of CD4 negative, CD7 positive T cells, CD3 negative, CD4 positive T cells, or CD3 positive, CD4 negative, CD8 negative T cells) and is thought to be secondary to these immunological disturbances. The disorder often exhibits are recurrent-relapsing course and is highly responsive to corticosteroids or rituximab as first-line therapy and interferon gamma as second-line therapy.

A lymphocyte is one of the subtypes of white blood cell in a vertebrate's immune system. Lymphocytes include natural killer cells (Phagocytes) (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). They are the main type of cell found in lymph, which prompted the name "lymphocyte".

A lymphocyte count is usually part of a peripheral complete blood cell count and is expressed as the percentage of lymphocytes to the total number of white blood cells counted.

A general increase in the number of lymphocytes is known as lymphocytosis, whereas a decrease is known as lymphocytopenia.

Health professionals must look at a person's history, symptoms, physical exam and laboratory test in order to make a diagnosis. If the results show patients with low levels of lymphocytes, absence of granulocytes or absence of thymus then the patient may be suspected to have RD.

A T cell, or T lymphocyte, is a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. They are called "T cells" because they mature in the thymus from thymocytes (although some also mature in the tonsils). The several subsets of T cells each have a distinct function. The majority of human T cells rearrange their alpha and beta chains on the cell receptor and are termed alpha beta T cells (αβ T cells) and are part of the adaptive immune system. Specialized gamma delta T cells, (a small minority of T cells in the human body, more frequent in ruminants), have invariant T-cell receptors with limited diversity, that can effectively present antigens to other T cells and are considered to be part of the innate immune system.

Basophils are a type of white blood cells. Basophils are the least common of the granulocytes, representing about 0.5 to 1% of circulating white blood cells. However, they are the largest type of granulocyte. They are responsible for inflammatory reactions during immune response, as well as in the formation of acute and chronic allergic diseases, including anaphylaxis, asthma, atopic dermatitis and hay fever. They can perform phagocytosis (cell eating), produce histamine and serotonin that induce inflammation, and heparin that prevents blood clotting. It used to be thought that basophils that have migrated from blood into their resident tissues (connective tissue) are known as mast cells, but this is no longer thought to be the case.

Basophils were discovered in 1879 by German physician Paul Ehrlich, who one year earlier had found a cell type present in tissues that he termed "mastzellen" (now mast cells). Ehrlich received the 1908 Nobel Prize in Physiology or Medicine for his discoveries.

The name comes from the fact that these leukocytes are basophilic, i.e., they are susceptible to staining by basic dyes, as shown in the picture.

The term "NK T cells" was first used in mice to define a subset of T cells that expressed the natural killer (NK) cell-associated marker NK1.1 (CD161). It is now generally accepted that the term "NKT cells" refers to CD1d-restricted T cells, present in mice and humans, some of which coexpress a heavily biased, semi-invariant T-cell receptor and NK cell markers.

Because CAPS is extremely rare and has a broad clinical presentation, it is difficult to diagnose, and a significant delay exists between symptom onset and definitive diagnosis. There are currently no clinical or diagnostic criteria for CAPS based solely on clinical presentation. Instead, diagnosis is made by genetic testing for "NLRP3" mutations. Acute phase reactants and white blood cell count are usually persistently elevated, but this is aspecific for CAPS.

Gene therapy is a relatively new concept in the field of SCID. This therapy is currently undergoing clinical trial and has cured a small number of children suffering from X-linked SCID and recessive allele SCID. Gene therapy aims to correct the underlying genetic abnormality in SCID. In the case of RD, the genetic abnormality would be AK2 malfunction. Stem cells are taken from an affected child's blood or bone marrow. Then in laboratory conditions the stem cells are manipulated and corrected with gene technology. They are then injected back into the patient. Similarly, in bone transplant, stem cells are able to find their way back through tracking mechanisms.

Research into AM functionality has been on the rise since AMs are one of the first lines of a defense against invasive pathogens. One of the most prominent fields is investigating liposomes as deliverers of antibiotics for treatment of respiratory intracellular infections. Intracellular parasites, such as M. tuberculosis, C. pneumoniae, L. monocytogenes, L. pneumophila, and F. tularensis, (to name a few) are taken up by AMs via phagocytosis, but are resistant to the biocidal mechanisms of AMs and can survive intracellularly, thus inducing severe respiratory infections. Pulmonary tuberculosis is caused by M. tuberculosis, and is now a major infectious disease worldwide and its incidence is increasing, especially in association with the AIDS pandemic. For sterilization of intracellular parasites in AMs, antibiotics are normally given orally or intravenously, but much of the antibiotics disperse to many different tissues, diminishing its effectiveness. Pulmonary administration of mannosylated liposomes is a much more direct, efficient route in targeting AMs; it enhances antimicrobial effect, reduces the dosage needed, and avoids unnecessary distribution to the blood. Since mannose receptors are exclusively expressed on the surface of AM, mannosylation of liposomes is an appealing approach to cell-selective targeting to AM. The efficacy of pulmonary administration of ciprofloxacin (CPFX) incorporated into mannosylated liposomes (mannosylated CPFX-lipososomes) was examined in rats, and determined to be an efficient means to target AMs.