CXCR4 is a chemokine receptor, which HIV utilizes as a coreceptor for entry into naive CD4+ T-cells and mature dendritic cells. Another chemokine receptor, CCR5 is used particularly for entry of HIV into immature dendritic cells, macrophages and activated effector or memory CD4+ T-cells.

The HIV envelope protein gp120 binds to CD4. This targets the virus to this T-cell subset.

gp120 is an envelope protein,  which binds to CD4 on the T-cell. Antibodies to the V3 loop of gp120 arise during the disease and are particularly effective as neutralising agents in vitro, although less so in vivo. Generally, neutralising antibodies are more effective against HIV-2 than against HIV-1.

CD8 numbers are largely unaffected. It is the ratio of CD4:CD8 that falls dramatically.

Lack of CD154 (CD40L) prevents signalling to the B-cell CD40 to bring about Ig class-switching away from IgM.

Production of cytokines and of cytotoxic T-cells are important in the protective response.

Here is no evidence that a high fat diet can lead to secondary immunodeficiency.

At least 10% of the population suffer to a greater or lesser degree from allergies involving localized IgE-mediated anaphylactic reactions to extrinsic allergens. An increasing number of these allergens have now been cloned including Der p1-14 from house dust mites and Lol p1-11 from rye grass pollen.

NK cells are spontaneously cytotoxic for certain tumor cell lines and express CD16, the low affinity Fc gamma RIII. Beige mice congenitally lack NK cells and die with spontaneous tumors earlier than their non-deficient heterozygous+/bg littermates.

Prostaglandins and thromboxanes are newly synthesised by the mast cell using the cyclo-oxygenase pathway. The leukotrienes B4, C4 and D4 (slow reacting substance of anaphylaxis, SRS-A) are also newly synthesised by the mast cell, in this instance using the lipoxygenase pathway.

Sodium cromoglycate is a mast cell stabiliser,  which makes the cell resistant to triggering. It is thus able to block type I hypersensitivity.

Carcinoembryonic antigen (CEA) is an oncofetal antigen but there is a high incidence of false positives. Reappearance of CEA after surgical removal of the primary tumor is strongly indicative of fresh tumor growth.

Another 15% of cases is due to RAG - 1/RAG - 2 defects.

Anti-CD33 is highly specific for myeloid leukemias in relation to other hematopoietic stem cells and has been used successfully for bone marrow purging and also for therapy.

Failure of regulatory T-cells would release the T-helper for direct stimulation by antigen. This statement is therefore incorrect, since this would not be a bypass of the T-helpers.